From their 4th album, Aftermath. Per pophistorydig, the song is about the funeral of a girl from her lover’s viewpoint, and he wants the color of everything to match his mood.

What’s with the comma in the title? Maybe they are saying “paint it, black!” like “hey, Mr. Black, please paint my door!” It was the record company’s idea to add the comma. Most compilations and internet radio stations remove the comma.
A cover of the music was used in the “Westworld” series aired on HBO directed by Jonathan Nolan and Lisa Joy.