You can spray them over anything, but to get the true color shift intended, they have to go over black. Makes for a pretty dark bait though. You can get really cool effects with other dark colors. I like to spray them over dark greens, reds, and blues. The combinations are endless. Over light colors, you get more of a standard pearl effect. I've found though, that it's much cheaper to add dry pearl pigment to clear base for those effects.