Dye and Mehndi

Hair dye

Q: Is it permissible to use permanent hair dye? Does it allow water to sink into the skin or does it just sit on the hair like a coating? Also if the hair dye contains alcohol, can I use it and then wash it out?

Black mendhi

Q: Someone has asked me to mix black mendi for them so they can apply it to the white hairs of their beard. I heard black mendhi or black dye is impermissable. So if I mix red mendhi with the black mendhi and make it dark brown will this be allowed?