When two colors look alike

Shift the colors a screen draws, so that a red warning and a green check mark stop looking like the same gray.

A green check mark means it went through. A red cross means it did not. A small red dot means somebody is waiting for a reply. If red and green sit close together for you, a screen keeps a certain amount of its meaning to itself.

Around one man in twelve sees red and green closer together than most people do, and rather fewer women. It is there from birth and has nothing to do with getting older — though a change in how colors look later in life is worth mentioning to an optician, since some causes are worth catching.

Every phone and computer can shift the colors on their way to the screen. Reds move away from greens, or the whole thing goes to shades of gray, or the display takes on a tint that suits your eyes. It is a filter over the light, exactly like a lens.

Key points

What to remember

Try this

On your own phone, look for Differentiate without color under Accessibility and turn it on, whatever you decide about filters. It costs nothing, changes nothing you can see straight away, and it means an app can never tell you something using a color by itself.

Practice: When two colors look alike. Your first lesson is free, with no account or card; the rest are part of a Lantern plan. Interactive lessons require JavaScript.

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