Color Matching can definitely be considered an art but it should also be considered a science. It is an art because there are only a few gifted number of people who have mastered color matching and it is a science because it takes some bit of knowledge to understand the chemistry behind colorants and how they are used in cosmetics and personal care products and how they interract with one another. These two facts make color matching a not so easy task to learn and excel in. Successful color matching requires experience, know how, time, and to become really fluent in color matching, patience. Not everyone can become a color expert. Either you have it or you don't.
By color expert I mean someone who can look at a shade, analyze it, evaluate it, and then decide what individual colorants are used to arrive at the shade. I say expert because it takes true talent to look at two shades that do not match and decide which and how much colorant will be needed to match the shade. In cosmetics, expert color matchers are few and far between.