I'm usually drawn to greens and purples - fortunately they look good together - and I love jeweltones -but a lot of times I'm doing a quilt with a particular person in mind, so I buy their favorite colors.
I did one for a young man whose favorite colors are orange (bright bright bright orange) and green (green green green green). I did a rail fence for him and teased while I was working on it that it looked like leprechaun puke - but it turned out surprisingly well and, more importantly, he loves it.
I read once that it's good to always pick a few colors that are out of one's comfort range. I don't much care for "earthtones" but I try to pick up a few now and again.