It's more common than you think, around 8% of males are colour blind. The red-green tag is mainly just the offical term for the type of colour blindess (as in not total colour blindess which does exist but is far rarer).
I personally, which I'm sure is true of others, have problem seeing the difference between similar colours/shades when they are close together. For example, if red (depending on the shade) and brown side by side they would look the same, the same with dark blue and purple, light green yellow/orange to name a few.
You would not know how frustrating it is with colour-coded puzzles in video-games and when using programs like Paint/Gimp when it comes to trying to get the right colour to use.
And yes....I can see traffic lights perfectly well before you ask!

Bookmarks