I don't use one, but most of my quilting friends say I have a good eye for color, or something like that. I don't have any education in art, other than what we had in grade and middle school.
One of my favorite things in past years has been participating in Bonnie Hunter's fall mystery - but I often dislike the colors she chooses and change them. I'm pretty confident in doing so. While most of my quilts these days are the scrappy style, even if cut from yardage, when I do use a specific palette, I can easily choose what I want. That's one of the benefits of having a nice stash to work with - I can pull and audition things against each other. That's my line and I'm sticking to it.