A color additive is any dye, pigment, or substance which, when added or applied to a food, drug or cosmetic, or to the human body, is capable (alone or through reactions with other substances) of imparting color. The FDA is responsible for regulating all color additives to ensure that foods containing color additives are safe to eat, contain only approved ingredients and are accurately labeled.

In addition, colors and dyes are used in textiles and we do require documentation for these as well. 
“Natural colors can be pigments derived from natural sources such as vegetables, minerals, or animals.” This is why we require detailed information on colors.