Hairstyle Color InspirationWant to color your hair like a pro? Then you´re going to need a little crash course on hair color theory. One of the foundations of hair color science is the hair color level system. The hair color level system is made up of ten different levels of hair color that range from one to ten. The number one represents black, the darkest your hair can be, while ten represents the lightest blond you can be while still having some pigment to your hair.