Contact your pediatrician and ask for a referral to an children's ophthalmologist to be tested. They have the card charts suitable for children to identify colorblindness.in addition, Check for family history to see if there is any pattern of color blindness on yours or your husband side of the family. If he is, don't be worried, color blindness is very common, and he will function fine.
Colour vision deficiency would exclude him from certain occupations like electrician, railway work, or certain jobs in the armed forces. If your son has the normal type of colour deficiency he will still be able to see colours, but will have difficulty distinguishing between certain shades of colour. You need not need to do anything otherwise, except help him choose clothes!
Told him matter of fact that he had a special way of seeing colors, it was't bad, it was just different, told him that if he was ever confused about colors, he could just say so, and ask for help, let he know that there were many people who were colorblind,it's nothing serious,and not a learning deficit.you also can began to learn more about color blindness. Traveling through libraries, bookstores and the internet. The most important goal for any parent I think, is to have a happy,confident child. I believe that you will make it.