Many color pigments cause skin sensitivity and irritation.  Absorption of certain colors can cause depletion of oxygen in the body and even death according to A Consumer’s Dictionary of Cosmetic Ingredients.  Debra Lynn Dadd says in Home Safety, “Colors that can be used in foods, drugs, and cosmetics are made from coal tar.  There is a great deal of controversy about their use, because animal studies have shown almost all of them to be carcinogenic.”