Maybe a dumb question (or at least one you've already considered), but, is there any color blindness in your family?
Tigers did a great job explaining color-blindness, but fwiw, just to throw in another color-blind family's experience - my dad was color-blind and so is my ds. DS knew his colors early on and could identify them. Color-blind people see color, they simply don't see the same color shades as non-color blind people. We didn't realize ds was color-blind until he was around 8 years old because he could tell us that green was green, even though he doesn't see green in the same color as I see green.
Even his school new he was color-blind from a screen in early elementary long before I did - the school assumed we (parents) knew and never bothered to tell us. We finally found out at a routine visit to the eye dr.
polarbear
