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.
Almost as important as the color choice is deciding how you will get there. Is this dye job a DIY project or will you put your tresses in the experienced hands of your colorist at the salon? The price tag can be considerably different depending on which direction you go.