Water Works Powder Hair Color, Permanent, 3 packs (Black)

do you use hot water? can u mix in paper bowl with plastic spoon? does cover white hairs, i am brown hair with patches of white, if use med. brown?

Where is the expiration date on this product?

does medium brown have some warmth to it? i do not want a dark flat look, i like a warm brown that has some lightness to it

What is the number on the package for?