Best answer. Hands down.
My first race play came as a surprise. I was deep fucking a new girlfriend and she suddenly yelled "Fuck your little white Bitch!"
I froze for a second but then really got into it.
If she had said "...with that n dick" or whatever, I would have paused a bit longer but I probably would have gone in extra hard.
*Everyone is different*. Know your playmate. She was getting off, and a girl getting off makes me thicken up. Can't help it. She knew me better than I knew myself at the time.
Every couple makes their own fucking rules. Telling someone whom you are not fucking what to do or not to do doesn't make sense.