I tell my patients that it should be called color confusion. As what happens is the color sensors of the retina are stimulated in a way that a few colors are confused, but the majority of colors are fine. In my experience, there are only a few tasks/careers that people with color "blindness" cannot perform.
Most of the patients that I diagnose with color "blindness" are adults when I diagnose them, and they have lived 20 or 30 or 40 years and didn't even know they had a problem. So, although he may wear a combination of clothes that you may laugh at, he shouldn't have any serious issues.
There are also devices which can help people with color "blindness," such as http://enchroma.com/
I hope this helps.
Best of luck.
Patrick Henry, OD