If you're in a contest, you'd better hope the judges are impartial. That means that they aren't biased toward one competitor over another.
If you’re partial to the color green, you love green and wear it all the time. If you’re impartial to colors, you don’t care what color you wear. To be impartial is to be objective, so you don’t mind one way or another how something is going to turn out. It’s important for jurors to be impartial when reaching a verdict, rather than allowing biases and preconceptions affect their judgment.