i think of "colourless" CZs
... i mean truly colourless ones. not the Asha, or Light Yellow, or Warm White, etc, but the true "D" colour CZs, like the regular white ChrisCZs, or Diamonique, Signity, etc....
i think of them like marshmallow fluff. it's white. yes? jar of white goop?
but do you know what's used to give it that white colour?
Blue #1.
so while being white, it's also blue... if that makes sense?
so i think of colourless CZs as being tinted with (the CZ equivalent of) Blue #1. so white that they're blue at times.
....but remember, too, that a well-cut stone will reflect what's around it. so if you're under a blue sky = blue reflection in the stone.