Three colors, not four

June 24, 2009 4:51 PM

A truly amazing optical illusion-- despite what you first think, there are only three colors in that picture.
posted by Chocolate Pickle (111 comments total)

Stupid fucking eyes.
posted by kbanas at 4:54 PM on June 24 [22 favorites]

It's not an optical illusion, it just looks like one.
posted by Confess, Fletch at 4:54 PM on June 24 [11 favorites]

Get out of my head.
posted by qvantamon at 4:55 PM on June 24

It's actually black and white
posted by gurple at 4:57 PM on June 24

Took me 10 minutes to see the unicorn, damn that's good.
posted by RajahKing at 4:58 PM on June 24 [4 favorites]

Well, colors are really just phenomena in our minds. So, if in my mind I perceive four colors, then there are four colors. There may be a smaller number of wavelengths of light or related physical phenomena. Nevertheless, there are four colors.

Now you might be thinking "well that's just from your perspective." True, but if we are discussing colors, then I have no access to any other perspective. In fact, trying to think about colors in some kind of putatively objective sense is likely to be nonsense.
posted by oddman at 4:59 PM on June 24 [7 favorites]

The overall pattern is a spiral shape because our brain likes to fill in missing bits to a pattern.

I love reading about the odd little illusions our brains play on us all the time, like this and how it fills in the blind spot where the optic nerve passes through the eye.
posted by frobozz at 5:00 PM on June 24

Could you stick that in a Powerpoint presentation, do a crazy flashing title screen with lots of !!!! in Comic Sans and email it to me? I can only look at optical illusions in that format. TIA!
posted by jontyjago at 5:00 PM on June 24 [9 favorites]

So maybe the visions I have of Krishna and his Gopis are just optical illusions? Or does this mean Krishna's skin is actually green, not blue (the Gopis' magenta saris confused me, perhaps)?
posted by kozad at 5:01 PM on June 24

jontyjago: I can spin that picture and put Donna and Fez jumping around in it. Does that help?
posted by qvantamon at 5:01 PM on June 24 [1 favorite]

sorry oddman: you're about to be heaped with abuse.
posted by kozad at 5:02 PM on June 24 [2 favorites]

The colors green and blue are interesting. In some languages there is just one word for green and blue--they are just different shades of the same color. Here in Japan, traffic lights are the same as everywhere--red, yellow, green (my emphasis)--yet that green light is called "blue" in Japanese.
posted by zardoz at 5:04 PM on June 24 [1 favorite]

I used to have a lumberjack shirt that was mostly a dark, forest green ... until a friend (rather high at the time) said to me, "You know, there is no green in that shirt."

This lead to closer inspection and sure enough, flecks of red and yellow and white, and lots of grey and black ... but no green thread anywhere in the shirt. Except if you stood back about five feet, it was a green shirt. No question. Everyone we asked agreed that it was, without hesitation.

Or like .Confess, Fletch. just noted ... It's not an optical illusion, it just looks like one.
posted by philip-random at 5:04 PM on June 24 [1 favorite]

Ugh, the aliasing, it burns. Could somebody make a decent vector version of this with proper antialiasing?
posted by Rhomboid at 5:07 PM on June 24

Or as Robert Anton Wilson pointed out.
posted by philip-random at 5:07 PM on June 24 [3 favorites]

I once painted a six-foot high 2nd Armored Division patch on a wall outside the National Guard armory I belonged to.

Where a black link of the track crossed from the blue field to the red field, from a distance it looked broken. I had to paint it broken, through trial and error, to get it to line up.
posted by atchafalaya at 5:12 PM on June 24 [2 favorites]

Isn't this really just a dithering effect, though?
posted by empath at 5:13 PM on June 24 [6 favorites]

Confess, Fletch: "It's not an optical illusion, it just looks like one."

That makes me think of..
posted by Plutor at 5:13 PM on June 24

Uh, you do know that there are really just three colors in ALL the pictures you see on your computer, right?
posted by nicwolff at 5:17 PM on June 24 [52 favorites]

Or, what empath said with less snark.
posted by nicwolff at 5:18 PM on June 24

There are four lights!
posted by Awakened at 5:19 PM on June 24 [7 favorites]

Despite what you first think, there is no chocolate in this pickle.
posted by kuujjuarapik at 5:24 PM on June 24 [1 favorite]

Anyone who has painted will have come across similar epiphanies. Although the stripes in that images are deliberately thin and confusing, using the dropper tool on apparently white buildings or white eyeballs in all manner of impressionist paintings will throw up all kinds of dull, dark and crazy colours. Colour relationships are incredibly important and maddingly hard to master with the naked eye. The work of Henri Le Sidaner for instance, is incredible.
posted by fire&wings at 5:30 PM on June 24 [3 favorites]

So, if in my mind I perceive four colors, then there are four colors.

And if you perceive sixcolors?
posted by ricochet biscuit at 5:32 PM on June 24 [4 favorites]

This means I'm not going to flight school.
posted by swift at 5:36 PM on June 24 [1 favorite]

So the next time someone swears they saw Jesus, or a UFO, or a ghost, show them this picture.

"Axesmith, will you grind this axe down for me?"
"What? I'm not an axesmith."
"Oh, then I guess I'll just have to grind it myself."
"What? Kid, get out of my shop."
"Hold on, just gotta grind this axe first."
"What? What are you doing?"
* grind grind grind *
posted by Greg Nog at 5:40 PM on June 24 [11 favorites]

Zowie.
posted by Durn Bronzefist at 5:40 PM on June 24

Rhomboid: With proper antialiasing the claim "there are only three colors in this picture" will no longer be true.
posted by aubilenon at 5:40 PM on June 24 [2 favorites]

Shit makes my head hurt, I don't care how many colors there are.
posted by PuppyCat at 5:44 PM on June 24 [1 favorite]

Technically speaking, green traffic lights in Japan are called "color-term-that-includes-colors-English-speakers-would-distinguish-between-as-green-and-blue." But that don't blow no minds.

And now in this thread, English speakers are failing to distinguish between green and blue when orange is nearby. I put it to you that the Japanese color system is way ahead of the game!
posted by No-sword at 5:45 PM on June 24

If you watch it really closely, you'll notice a gorilla walk through.
posted by cog_nate at 5:50 PM on June 24 [11 favorites]

Wow, fire&wings, thanks for the tip on Henri Le Sidaner - amazing.
posted by twsf at 6:00 PM on June 24 [1 favorite]

The colors green and blue are interesting. In some languages there is just one word for green and blue--they are just different shades of the same color.

Mr. Lucinda and I had an ongoing argument as to the color of one of our cars. I insisted it was blue, he insisted it was green.

(Even though the car company called it "Elegance Green", it *was* blue. Really.)
posted by Lucinda at 6:05 PM on June 24

trying to think about colors in some kind of putatively objective sense is likely to be nonsense

and yet "the RGB colors in both spirals are 0, 255, 150" seems so unambiguous.
posted by stupidsexyFlanders at 6:06 PM on June 24 [6 favorites]

Sorry, but if you see a color, it counts as another color. Mind trumps science every time.
posted by Zambrano at 6:11 PM on June 24

Do the Japanese have RBB monitors too?
posted by SpaceBass at 6:15 PM on June 24 [3 favorites]

Pro tip: Mac users, hold the ctrl key and mousewheel up to zoom in on the picture and see the pixels for yourself. Personally, I needed that kind of verification to really believe this thing.
posted by martens at 6:16 PM on June 24

Mr. Lucinda and I had an ongoing argument as to the color of one of our cars.

People that have cause to write down the color of my very tan truck say that it is silver as often as not. This confuses me. They make silver F-150s. I don't have one.
posted by flaterik at 6:16 PM on June 24

zardoz: "yet that green light is called "blue" in Japanese."

Is that because there's no disctinct words for "blue" versus "green" in the entire Japanese language? Or just that a green light is called blue, in a weird twist of historical legacy?

That reminds me of Berlin and Kay's 1969 theory of color word evolution, refined in 1999 by Kay and Maffi.
posted by Plutor at 6:21 PM on June 24

mind: blown.

Also, to continue the derail about Japanese colors, colors like green, yellow and orange are new to the language. There used to be only 4 words to represent colors - 白(white) 黒(black ) 赤(red/yellow) 青(blue/green). This is why the color of the sun is said to be 赤 (aka) and there are places like 青森 (aomori or blue forest).
posted by mexican at 6:28 PM on June 24 [4 favorites]

Some good ones here. My favorite is the Koffka Ring.
posted by grumblebee at 6:29 PM on June 24 [1 favorite]

I have witnessed (okay, and participated in) very animated...discussions with bird watchers trying to figure out if a bird's legs are pink, yellow, or orange.
posted by rtha at 6:31 PM on June 24 [1 favorite]

Another good demonstration of the effect of context on color and why you should develop your whole painting from simple to complex, rather than polishing one area and moving on.

http://www.digitalartform.com/archives/2005/06/color_judgement.html
posted by jfrancis at 6:35 PM on June 24

I think the illusion here is more related to this than it is to dithering.
posted by invitapriore at 6:37 PM on June 24 [1 favorite]

I once painted a six-foot high 2nd Armored Division patch on a wall outside the National Guard armory I belonged to.
"this patch was worn over the left chest pocket of the fatigue and camouflage uniforms rather than on the sleeve..." I'm sure their foes appreciated the colorful "shoot here" patch right over their hearts.
posted by kirkaracha at 6:40 PM on June 24

It's not just a color issue, it's context. We're pattern-finding machines.

A similar, well-known example using just gray.
posted by rokusan at 6:52 PM on June 24

Plutor: They're called a word that refers to the color they are, as well as other colors such as the blue of the sky etc. There are other words that refer to blues and greens more specifically, but there's no reason to use them. (Unlike if, say, traffic lights were red, blue, and green.) It's not that people can't distinguish between green and blue here, there's just no pragmatic reason to in this case.

(Like Mexican says, it's about relative recency. Really interesting topic!)
posted by No-sword at 7:03 PM on June 24

Actually, there are four colours. There's a black pixel in the middle.
posted by krisjohn at 7:03 PM on June 24 [1 favorite]

This one has always blown me away, too. But at least I understand it.
posted by Chocolate Pickle at 7:13 PM on June 24

For my money Greg Nog wins this one. It's like, "Here's an optical illusion. Fooled you, didn't it? THERE IS NO GOD!"

It's a cool illusion, but it doesn't demonstrate a thing about ghosts or anything like that that hasn't been proven thousands of times already by stage magicians.
posted by JHarris at 7:28 PM on June 24 [3 favorites]

... there is no chocolate in this pickle.

That's what you think. (MWAAAhaaahaaa!)
posted by Chocolate Pickle at 7:28 PM on June 24

Phil Plait is awesome. Thanks for sharing!
posted by futureisunwritten at 7:36 PM on June 24

"and yet "the RGB colors in both spirals are 0, 255, 150" seems so unambiguous."

Answer 1: Yes, but then it's no surprise that seemings are sometimes misleading.

Answer 2: Well, a lot of nonsense is unambiguous.

Answer 3: The phrase "RGB colors" happens to sometimes correlate to color perceptions in our minds. If we accept, for the sake of argument if nothing else, that we can talk about RGB colors as objective features of the world, this does nothing to imply that our respective occasionally-correlated experiences are any less subjective or any more subject to correction by people who claim privileged knowledge.
posted by oddman at 7:40 PM on June 24

way cool.

sorry, i mean: waaay cool.
posted by jammy at 7:41 PM on June 24

I like this kind of stuff. Thanks for the link.
posted by box at 7:51 PM on June 24

Mind trumps science every time.

I think not.
posted by Lentrohamsanin at 7:59 PM on June 24

The Jesus/UFO/ghost thing isn't so much out of left field, considering the author of this blog is the president of the James Randi Educational Foundation, which of course does a lot of phenomena-explaining. So. That's something.
posted by tepidmonkey at 8:02 PM on June 24

Did anyone link to the chessboard illusion yet?
posted by knave at 8:10 PM on June 24

considering the author of this blog is the president of the James Randi Educational Foundation

Prove it.
posted by East Manitoba Regional Junior Kabaddi Champion '94 at 8:32 PM on June 24 [1 favorite]

here - all we have here is sky
all the sky is is blue
all that blue is is one more colour now
posted by bwg at 8:46 PM on June 24

I love the irony of him pointing out how our minds can be tricked into misinterpreting things, and then assigning this simple optical illusion with tags like Antiscience and Skepticism. A very thorough lesson on psychological projection, to be sure!
posted by hermitosis at 8:49 PM on June 24

and yet "the RGB colors in both spirals are 0, 255, 150" seems so unambiguous

As anyone who's worked with color in a technical way would tell you, it actually is pretty ambiguous— but saying what the XYZ tristimulus values are would also not explain this illusion.

Japanese is not the only language/culture that has a different set of "basic" colors. Some have fewer than English does, some have more.
posted by hattifattener at 9:11 PM on June 24

TIME FOR SOME ROTATING SNAKES
posted by brain_drain at 9:12 PM on June 24 [4 favorites]

I like to think that, as a society, we are color blind.
posted by Evilspork at 9:18 PM on June 24

With proper antialiasing the claim "there are only three colors in this picture" will no longer be true.

Yes, true, on the one hand you couldn't make that claim. But the illusion would still be just as valid and it wouldn't have to look like complete ass. Bonus: With a vector version you could have a zoomed version (even with no antialiasing, so as not to confuse the issue) that still had sharp edges without looking like something that was coughed up by a 1988 Nintendo.
posted by Rhomboid at 9:24 PM on June 24

TIME FOR SOME ROTATING SNAKES

IT IS NEVER TIME FOR THAT.
posted by TwelveTwo at 9:28 PM on June 24 [11 favorites]

well, the mind was not meant to interpret flat colors on a 2-d plane, period, it's just not what it was designed to do.

It's interesting that we stare at completely fucking miraculous optical illusions all day long and they're so commonplace that we never even comment on them any more (perspective in oil paintings, photographs, motion pictures, video games, 3d movies). It takes something really abstract or novel for us to notice any more.

For example, the spiralling snakes one -- 'These snakes are NOT animated", everyone I've shown that to has been wowed by it. And yet we don't comment on the mind's ability to be tricked into seeing a plain old animated image as a moving object any more.

How many of us saw watch movies and really think about what's going on in our brain while we're watching it. It's just colored shapes projected on a screen, and yet we use them to build an entire internal model of a world. We're not just watching an image on a screen, we're creating an entire reality while we're watching it, modelling character motivations, making predictions of the behavior of moving objects on the screen, etc, just as if we were watching it in real life. We intepret all of it as reality, and we can't help ourselves from doing it.

Try watching a movie and only see it for what it really is. A white screen with light projected on it. I'm pretty sure you can't, or you can't easily do it.
posted by empath at 9:58 PM on June 24 [1 favorite]

I think everyone reading this thread needs to click, "make it start"
posted by edgeways at 9:58 PM on June 24

God damn wikipedians have a lot of time on their hands.
posted by delmoi at 10:02 PM on June 24 [2 favorites]

IT IS ALWAYS TIME FOR THAT.
posted by davejay at 10:03 PM on June 24

Try watching a movie and only see it for what it really is. A white screen with light projected on it. I'm pretty sure you can't, or you can't easily do it.

Try watching 'Spanglish'.
posted by mazola at 10:05 PM on June 24 [4 favorites]

An wonderfully weird illusion. For my money, the freakiest optical brain**** is the McCollough effect, a weird coupling of color perception and edge orientation that is induced by staring at an "induction image" for a few minutes...but can last for days, weeks, or even months.
posted by madmethods at 10:14 PM on June 24 [3 favorites]

Japanese is not the only language/culture that has a different set of "basic" colors. Some have fewer than English does, some have more.

Yup, take Russian for example which differentiates between dark (navy) blue and light (sky) blue. It seems like an arbitrary distinction until you consider that we differentiate between red and pink in English, when pink is really just a lighter shade of red.
posted by pravit at 10:18 PM on June 24

Wow. WOW. Great illusion.

All y'all Sapir-Whorf acolytes who think that there's something deep about different languages having different color words are barking up the wrong tree. It's not relevant to this illusion. Though color perception is affected by context, it's all still really low-level. Linguistic influences and cultural biases just don't penetrate that deeply. Native Japanese speakers (or whoever) would still experience the effect of this illusion.
posted by painquale at 10:31 PM on June 24

Uh, you do know that there are really just three colors in ALL the pictures you see on your computer, right?

that was before i saw tub girl and threw up on my monitor
posted by pyramid termite at 10:34 PM on June 24

i had a book on color once (called "color"...try linking to that on amazon) that had a series of identical colorspaces (like a color wheel but with black and white and brown and all the color's tints and shades, and not in distinct circles, but all blended together), one for each culture, with that culture's color definitions circled. it was fascinating. a lot of cultures don't differentiate 'orange' from 'red', and a bunch consider it part of 'brown'. gawd i wish i could find that book...it had a really cool dust jacket, mostly black, with metallic foil embossed prismatic concentric squares in a broken grid, shaded with the spectrum...veerrry groovy.
posted by sexyrobot at 10:49 PM on June 24

Was it the Time-Life one?
posted by Rhomboid at 11:39 PM on June 24

Incredibly, the green and the blue spirals are the same color.

No they're not.

Next!
posted by pompomtom at 11:55 PM on June 24

Was it the Time-Life one?

maayybe...but not that one. i've seen that one...it has a stereographic cover...it might have been time-life, but it wasn't about 'color photography', just color in general...and it was just called 'color'. dammit this is driving me craaazy. OMG I'M SCREAMING AT GOOGLE! no not any other words!!! JUST COLOR!!! GODDAMMIT FUCKYOUEVERYWEBSITEFUCKYOU!!! deep breaths. amazon returned about 200,000 results with crap on the front page like 'feng shui color in your living room'. i'm going to bed.
posted by sexyrobot at 1:21 AM on June 25 [1 favorite]

Actually, there are four colours. There's a black pixel in the middle.

Black is not a color.

I'm sorry.
posted by Dr Dracator at 2:55 AM on June 25

Which are you going to believe? What you read on the Blue, or your own lying eyes?
posted by Tuesday After Lunch at 3:06 AM on June 25

TIME FOR SOME ROTATING SNAKES

IT IS NEVER TIME FOR THAT.

IT IS ALWAYS TIME FOR THAT

THAT'S IT. I HAVE HAD IT WITH THESE MOTHERFUCKING SNAKES IN THIS MOTHERFUCKING THREAD.
posted by elfgirl at 5:08 AM on June 25 [5 favorites]

I'm sorry.
posted by elfgirl at 5:09 AM on June 25 [1 favorite]

If you stare at that optical illusion for 30 seconds, then stare at the sun for 5 minutes, then back at the illusion, you will no longer see any differences in color.
posted by orme at 5:34 AM on June 25 [2 favorites]

About those rotating snakes.....I've been looking for a while for a print of this to hang on the wall. Anyone know if such a thing is available?
posted by Yer-Ol-Pal at 5:56 AM on June 25

These ridiculous gelatinous orbs!

(OK, in this case it's probably the neural processing behind the orbs, not the orbs themselves. But still.)
posted by DevilsAdvocate at 6:06 AM on June 25

THAT'S IT. I HAVE HAD IT WITH THESE MOTHERFUCKING MONKEY-FIGHTIN' SNAKES IN THIS MOTHERFUCKING MONDAY TO FRIDAY THREAD.

FTFY.
posted by EarBucket at 6:08 AM on June 25

More optical awesomeness.
posted by HumanComplex at 6:48 AM on June 25

color is a secondary quality, and therefor only exists in my mind. My mind sees four colors.
I've read my John Locke.

for that matter, I've read my Bishop Berkeley too, and all of this exists only as a perception in my mind.
posted by Flood at 6:50 AM on June 25

huh - the digital colormeter on my mac says that the "example squares" he uses in the article have different RGB values (0, 255, 127) from the actual blue in the illusion (0, 255, 150). /pedant
posted by R_Nebblesworth at 7:05 AM on June 25

never mind, a commenter explained it.
posted by R_Nebblesworth at 7:07 AM on June 25

Flagged. This isn't appropriate for AskMeFi. Take it to the blue.
posted by kittyprecious at 7:31 AM on June 25 [6 favorites]

Beans here, gotcha' plate o' beans here!
posted by SteveInMaine at 7:49 AM on June 25

empath How many of us saw watch movies and really think about what's going on in our brain while we're watching it

How many of us watch life and really think about what's going on in our brain while we're watching it? People talk about 24 frames per second movies being a shocker as if real life is infinity fps. The reality is a discrete number of photons of light are hitting our eyes, getting converted into a discrete number of electrical signals that propagate through our brain and are somehow processed as they do and merged into a smooth, holistic mental picture full of large-scale concepts and entities

We're not seeing faces or smelling coffee or feeling a warm shower or hearing music, we're just processing electrical signals in our brain into some sort of picture of the world. This gets into the philosophical question of qualia - why and how and what they are
posted by crayz at 8:11 AM on June 25

Somete30mes... metafilter is BLUE, and sometime it's WHITE.... whatgives?!?!?! It *magically* changes color after I type my debaser neam in... Sooooooooooooooooo weird!!!11!!!.+!3! you shouldcheckitout! i have scrnshoots on my homepage!!!!!1111

www.angelfire.com/whereismybloo!
posted by Debaser626 at 8:13 AM on June 25

Isn't this really just a dithering effect, though?
posted by empath

No. There is a dithering effect as the design gets closer to the middle, but it has nothing to do with the green/blue illusion. There are no geometric differences in the aqua spirals. The geometry leads us to believe that the same stripes are crossing them, but in fact, alternate aqua spirals are crossed by orange, then magenta stripes. The aqua background appears to take on the complementary hue of the stripe. The complement of magenta is green, and the complement of orange is blue, so the aqua appears different in each case.
posted by weapons-grade pandemonium at 8:26 AM on June 25 [1 favorite]

Um, is it just me, or are those lines outlined in red & blue?

Zoom in as far as possilble. Look at the orange lines as they pass through the purple. Outlined in red, no?

Look at the green lines as they pass through the purple (or purple lines as they pass through the green). Outined in blue, no?

Also, the boundary between green & purple spirals is bordered with blue, while the boundary between "blue" and purple spirals has no border.

Is it just me? Is my computer screen defective? Or are there five colors, not three?

I think someone's screwing with us.
posted by philotes at 9:00 AM on June 25

It's just you. But if you zoom in to max, the illusion more or less disappears--you can see that the blue and the green are actually the same aqua hue.
posted by weapons-grade pandemonium at 9:15 AM on June 25

Is this something I'd have to have normal color vision to understand?
posted by ActingTheGoat at 9:15 AM on June 25 [1 favorite]

I have a feeling that when I finally break from reality and totally embrace my madness, looking at things like the Rotating Snakes illusion is what the forensics people will identify as having been the cause.
posted by quin at 9:16 AM on June 25

Nonsense. I can clearly see dark orange pixels, speckles of grey, a peppering of black, and random bursts of teal, purple, white, maroon, burgundy, and fuchsia. All I had to do was save it as a JPEG.
posted by TimeTravelSpeed at 9:23 AM on June 25 [1 favorite]

Zoomed in as far as I can and there they are, red and blue outlines, plain as day (though I can see that the blue/green is always the same blue/green - no problem there). Stupid Internet Explorer. Maybe when I get home I'll look at it in Firefox and zoom in til the whole image becomes a dancing screen of 0s and 1s.
posted by philotes at 9:48 AM on June 25

The colors of course actually ARE blue and green proving once again you shouldn't believe everything you read on the internet.
posted by Muirwylde at 10:10 AM on June 25

I thought I was going to see a scorpion or something in the image...
posted by EdwardFresco at 11:56 AM on June 25

go here and tell me what color the background is! Wait a sec... Wait a sec... ok, now? and now?
posted by Nauip at 12:06 PM on June 25

"So the next time someone swears they saw Jesus, or a UFO, or a ghost, show them this picture."

Jesus?
posted by Smedleyman at 1:18 PM on June 25

So I put the image in MS paint. And then I used the magnifying thing. Those colors are exactly the same.

End of argument.
posted by parm=serial at 5:03 PM on June 25

OK! New argument: what does it mean for two colors to be the same?
posted by oddman at 9:45 AM on June 26

It means that although the colors may appear subjectively different in different contexts (with different illumination and/or backgrounds), they will absorb and reflect identical wavelengths of light from a full spectrum light source. If the tie you are buying matches your suit in the store but turns more red outside, it is because there was little or no red (low frequency) light in the store, but under full spectrum light (sunlight) it becomes apparent that the tie and suit are not really the same color. If you want a match, compare tie and suit in sunlight. Reflected colors are selective echoes--the color is not "in" the tie--it is in the light.
posted by weapons-grade pandemonium at 11:12 AM on June 26

In the case of color coming from a light source, like your monitor, it means the same frequencies are emanating from those pixels.
posted by weapons-grade pandemonium at 11:16 AM on June 26

I'd be really curious to see how one would perceive a version of this made like the mirrored version at the very bottom of this page, but with adjacent squares having the pink and orange stripes reversed. So the stripe that looks green one one square meets a stripe that looks blue on the next.

Seems possible that the places the colors meet look different from either side, or it could even break the illusion entirely, but I doubt that. I may have to spend some time tweaking the file and see what happens...
posted by polymath at 9:33 PM on June 26