Question

Why are pimples white or black

Answer 1

Pimples that look the color white are called White-heads.
Pimples that look black are called Blackheads. 
White heads are infected pimples and they are filled with pus. If you pop them, you'll cause the area to become more infected, thus you will most likely have more of them. 
Black heads are your pores being block by dead skin cells and dirt. The dirt makes it look black. 

Good luck~

Answer 2

Because the white ones have pus and the is just a like white kind of cream color. the blacks are called blackheads btw