A good color means natural. Look carefully at a fistful of hair in the mirror. See how each strand has a different tone? Perhaps even different colors on one strand? These are the natural striations that Mother Nature gives each head of hair to work with natural lighting. A good "color job" must duplicate these natural highlights to be effective.
Still if that sounds at all appealing you might first want to stop and ask yourself some questions. Or at least think about these points which can help you decide among the many hair color options. Since the goal is find out which will actually work out best for you and your hair.