Whats "impaired" color vision?

Imperfect perception. Impaired color vision is when a persons color perception is more limited than a "normal". The degree of impairment is related to the degree of inability to distinguish color differences. There are good tests to make this determination. in your ophthalmologist;s office.
Color bindness. There are several different levels and severities of color blindness. You can have red-green or blue-yellow blindness and they can be partial or complete. The only way to know is to have color vision testing by your ophthalmologist.