V. Stiviano Porn Offer -- Have Revenge Sex On Tape With Black Guys

V. Stiviano can now loosely take Donald Sterling up on his offer ... allowing her to have sex with black guys.

Vivid Entertainment honcho Steve Hirsch has sent V. a letter ... offering her a starring role in a sex tape with, as he put it, "the most well-endowed black men in the porn industry" -- which as you know is really saying something.

But Hirsch understands one thing for sure -- 15 minutes of fame. He's given V. 24 hours to make her decision.

We're sure she gets the drill.