I've dyed my hair (naturally champagne blonde) with blue stripes, and also solid purple and solid black. I want to try dying the ends green
I'd like to try pink, but I think my natural hair color is too dark to go well with it. My sister has chocolate brown hair that looked amazing with bright red ends.
I'd say if you are fair-skinned, pastel colors look better than vivid. It's easier to pull off bold colors if you have darker skin tones (olive, etc) in my opinion. Take into account your eye color, too