Tile Grout, Plaster Color

[Gmilich]

Hi,

We are in the process of renovating our in ground pool.
We picked out dark blue 6x6 tiles and diamond brite blue quartz. We would like to get a natural feel to the pool. Coping is cobblestone. Our contractor recommendations only white grout for the tiles because a color like gray may run down on the white plaster. Have others run into this issue?
We want to then consider a gray plaster, Diamond brite French Gray and were told it can show cracking... not sure what to do, any suggestions?