Not sure if it's needed, but fancy stones, like radiants, pears, emeralds, Assschers, ovals, luceres, etc, which are not particularly known for superb sparkle like a round show color MUCH easier.
In radiants, I can see the color difference on an F to D. Meaning, you give me a loose stone, with nothing to compare it to, I can call it's color, even in colorless. But you give me a well cut round stone, and I can't tell an H from a D. Sparkle factor also makes your rounds look whiter, so try the lower colors in better cuts!