I haven't really noticed a difference. However, there are times when I think a bait that has some flake in it will work a little better, especially during late Spring when fish are aggressive and active. But that's minor. Furthermore, I refuse to throw a bait that has metal flake in it in cold water. If you notice everything around you when the water is cold and the air temperature is cold, everything is bland/dull; not lively. So during those times I prefer green pumpkin, brown, or even plain black.
"If people concentrated on the really important things in life, there'd be a shortage of fishing poles." - Doug Larson