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?
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.