If my wife must go into work on Tisha B’av for a couple hours, Is she allowed to put on makeup?
Women should not put on makeup on Tisha B’av, and the reason is because on Tisha B’av we are not allowed to annoint ourselves. Applying makeup, perfume, or using soap are all examples of annointing.
NItei Gavriel 73-5, in the name of R’ Moshe Feinstein Zt”l. Also see 31-5.