That's what being colourblind is like. I have three friends who are colour blind, all to a different degree. Two of them just get minor shades mixed up, like light green looks like tan, or something like that. But the other one sees totally different colours. Green is purple, orange is blue, yellow is red, and vice versa.

Funny that we wouldn't even know we were colourblind if it weren't for the education system, or the eye doctor I guess.

PS - Remember the circle with the number in it that they use for testing colourblindness? For his birthday last year, we bought him a shirt that was like that, except instead of a number inside of it, it says "Fuck the colour blind." He still doesn't know what it says..