Any good tattooer will probably tell you that:
#1 They will not do a white only tattoo
#2 They will not tattoo your palms or hands(unless you are a tattooer or "heavily tattooed", whatever the requirement is for that...Generally, at the shop I work at, we don't tattoo hands, faces or necks unless you already have previous tattoos in one of those place or you are a tattooer.)
#3 White pigment turns yellow over time and basically looks like dried skeet
Your hands exfoliate a lot and the skin there acts way differently than other places. A responsible tattooer will explain to you the subtleties of this. Most notably, anything on fingers, hands, and palms, will fade quickly and not look very good. The issues with skin combined with the fact that white ages into a sort of yellow when by itself should be enough to make you think twice about this. I see a whole lot of people come in looking for white tattooes and after someone explains the problems to them, they usually change their tone.