Natural hair color, eye color, skin tone and age are all factors that determine which hair dye is best for a person. Generally, the appropriate dye complements one's physical characteristics, rather than overshadows them.
There are two main skin tone categories: cool and warm. People who have naturally blond hair usually have cool undertones, while people who have naturally brown or black hair typically have warm undertones. The perfect dye often correlates with one's undertone. Ash blond and auburn brown are hair colors that suit those with cool skin; golden blond and honey brown are hair colors that suit those with warm skin. Older people usually look better with lighter hair colors.