You should use the clay that is gray. The gray clay when fired in the kiln turns white. Perfect skin tone for Edward Cullen. ^_^. Don’t use sandstone clay or that yellow color clay because it will become flesh pink (ugly color) or that regular flower pot color when fired.
Hope this helps. I forgot what the gray clay was called but make sure it has not been mixed with any other clay as that would take away the white finish you get after firing your piece. I used to recycle clay by mixing gray and yellow together and when fired that clay becomes a light pink ranging to a pink depending on how much gray clay and yellow clay (sandstone) is in the mix.

hes white whit and ya!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!