I can hardly imagine that there could be a different result due to the color of a player's skin. The fact is that many people from all over the world follow the matches very closely. I’m now talking about well-known leagues, for example in football. So, because of one such mistake, a judge or his assistant may lose his job forever and a huge scandal may result.
I cannot say that this has never happened or will not happen, but I can say that I do not know of such cases. Maybe somewhere in the regional leagues
I don't think @OP mean racism is about skin color, but it's more like to nationally or teams. If skin color is the problem, there will be a lot discussion about that, but I had never heard about about such case.
Actually it also happen on well-known leagues, surprisingly the referee didn't get any sanctions and still become referees in top leagues.
Neymar's rainbow flick is one of the example. there's nothing wrong with that, but since English players can't do that, they ban rainbow flick and give yellow cards for anyone that do that.