should I be concerned about colorblindness?

I think colorblindness is not being able to see the difference between red and green so he must just have the names mixed up. He'll sort it out with some discrete parental observations like "Oh look at the yellow flowers" or "the sky sure is blue, today". I don't think it is a good idea to directly correct young kids about such things. It could squelch their self-assuredness which is a precious thing.

FWIW, my niece, who is certainly bright, didn't really learn her colors until she was almost four.

Yea my guess is hes just mixing up the colors. He'll get it
Deanna

My dad is color blind (totally red/green color blind -- he sees them all as a murky brown/grey) which means that each of my boys has a 50% chance of inheriting it from me (I am not color blind but carry the gene.) There are different degrees of color blindness. My oldest ds has been diagnosed as "color blind" though he can see the primary shades. He can see red and he can see green, but as you get into the different shades, he can't tell them. It was diagnosed at a school eye exam and I was a bit surprised because he had passed the really basic test they gave him at the opthomologist. Strange, huh. The test they gave him at school and then the next time I took him to the pediatrician was much more comprehensive as far as colorblindness goes.

We also suspect that my second ds may also be color blind to a point, but at his last pediatrician exam they couldn't be sure if he was, or if he didn't know all the numbers used in the test.

It hasn't been a problem for my oldest son at all. He never told us colors incorrectly and new them all by the time he turned two. It hasn't affected him at all.

The only way it affected my dad was that he sometimes needed help making sure his clothes matched (he used to ask if the "grays" he had chosen went together), and he owned a hair salon but didn't do any coloring -- after all, who wants a color blind colorist.

My guess is that since your dc calls blue yellow, and vice versa consistenly, she is just mixing up the names. If she were to call shades of blue, blue sometimes and yellow sometimes then it sounds more like a degree of color blindness, but if she is using the same word for the same color each time, it's more likely that she is seeing the color the same, but has just assigned a different name to that color.