Myths

Colour myths, checked

Ten common ideas about colour, checked against the sources.

How this site works. Every fact is in our own words and linked to its source, beside it. Where good sources disagree, we show each version in a “Sources differ” box. Every picture is our own drawing: we don’t copy the famous originals, we make our own versions of the idea.

1. MythThe dress photo shows who is colour blind.

   FactIt has nothing to do with colour blindness. Michael Bach

2. MythThings look red because they send red light to your eyes.

   FactThere is not a single red, or even reddish, pixel in it. Michael Bach The mostly green-blue picture shifts what your eye takes as white, so grey and white areas look reddish. Michael Bach

3. MythThe same grey always looks the same.

   FactIn fact the two squares have identical luminance: the same amount of light comes from each. Michael Bach His law of simultaneous contrast: colours placed side by side affect each other, each pushing its own complementary colour onto its neighbour. Britannica

4. MythYour eyes measure light like a camera.

   FactOur eyes are not light meters: they take context into account. Michael Bach Your brain estimates the lighting and judges the material: is this a light or a dark square, whatever the shadow? Michael Bach

5. MythA colour can only be where it is painted.

   FactIn the watercolour illusion, shapes edged with a dark wavy line and a lighter coloured line inside look faintly tinted, though the inside is plain white. Michael Bach In Bach’s assimilation demo three discs behind coloured grids look cyan, magenta and yellow, but all three are white (strictly, a light yellow). Michael Bach

6. MythAfterimages mean something is wrong with your eyes.

   FactA common one is the spot you see after a camera flash. Britannica An afterimage normally fades within a few seconds. Michael Bach

7. MythRed’s opposite colour is green.

   FactBach notes that the opposite colour of red is not green, as many textbooks say, but blue-green. Michael Bach The reddish surround pushes the grey towards its opposite colour, which for red is blue-green. Michael Bach

8. MythA camera would see the colours on Benham’s top.

   FactTake a photo of it spinning and the colours are not there. Michael Bach

9. MythScientists have explained every colour illusion.

   FactNobody knows for certain why the colours appear. Michael Bach Bach admits he doesn’t understand the brain mechanism behind assimilation. Michael Bach

10. MythEveryone sees colours exactly the same way.

    FactJay Neitz, who saw white and gold, said that in 30 years of studying colour vision it was one of the biggest individual differences he had ever seen. WIRED Colour names play a part too: a bright, bluish colour counts as ‘white’ for some people and ‘blue’ for others. Michael Bach