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February 22, 2010

Can you see bluish yellow or reddish green?

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While at the airport on my way to Chicago last weekend I picked up the Feb issue of Scientific America. It’s always a good read and I was particularly intrigued by an article on impossible colors, colors that we are not supposed to see. Can you imagine a reddish green (greenish red) or yellowish blue (bluish yellow).

You can read about the theory here but cut to the chase and do these simple tests below to see the colors for yourself.

  1. Click on each of the graphics below, this will bring up a much larger image in a new browser.
  2. Hold a finger in front of your nose and focus intently on it. This will cross your eyes.
  3. Slowly remove your finger from view
  4. On your screen you will see three boxes. The middle box will show the impossible color, a bluish yellow or a reddish green. Make sure the crosses line up.

Can you see yellowish blue?

bluish yellow

Can you see reddish green ?

reddish green

It took me a while to master the visualization technique but it is a bit like doing the magic eye pictures. The key to seeing the colors is to hold the cross steady. They are pretty unstable and seem to flick in and out but they are definitely colors I have never seen before.

How about you, can you see them?

2010 © St Louis Web Designer

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5 Comments on Can you see bluish yellow or reddish green?

  1. Clay Anderson on Tue, 9th Mar 2010 9:22 am
  2. Actually, they're not new colors. Bluish yellow = green, and reddish green = yellow (or in your example, closer to orange), just as you'd expect.

    The only reason they look any different is because our eyes only do a moderate job of mixing the two colors, flickering back and forth between giving each eye (and therefore, color) dominance.

    You can produce a similar effect by interlacing (alternating lines) the two colors in Photoshop.

  3. St Louis Web Designer on Tue, 9th Mar 2010 12:57 pm
  4. Thanks for stopping by and trying this out Clay.

    I beg to differ on the colors though. When viewing the bluish yellow example I see a weird color that is definitely not green.

  5. Adrian on Tue, 9th Mar 2010 10:23 pm
  6. Actually I think Clay is also wrong. Yellow and Blue, If our eyes did a better job of mixing would be white.

  7. shoebappa on Sun, 21st Mar 2010 11:04 pm
  8. This was a fascinating thought process. Initially I thought exactly what Clay is describing, and was curious about the lack of agreement.

    When I looked at this I didn't see blue and yellow making green, but the interlacing and flicking back and forth is precisely what I saw.

    I did some experiments in a graphic program:

    The 1st column the first color, 2nd an interlace (1 pixel of one followed by one pixel of another) of the 1st and 3rd columns. The 4th column is the color with 50% of the other overlayed (digitally mixing them).

    If your browser scales images automatically, you may not see the interlacing well without viewing full sized, but it is fascinating to watch the browser scale the interlacing down to the mixed colors in the 4th column.

    This turns out to be because it scales images poorly, but so does everything else apparently (

  9. St Louis Web Designer on Mon, 22nd Mar 2010 8:57 am
  10. Thanks for your comments Adrian and Shoebabba.

    Interesting graphic from Shoebabba's comment.

    Here is the clickable link


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