If you successfully design your C++ hiring criteria to be colorblind — to not notice the color of weasels, but only to notice how good they are at C++ — then performance on the hiring criteria will shadow weasel color as an indicator of C++ ability.

You might end up with 99 blue weasels hired for every one red weasel hired; but you will have successfully filtered out all the red weasels that are bad at C++, just as you successfully filtered out all the blue weasels that are bad at C++. After all, only a tiny fraction of blue weasels meet your C++ hiring criteria, too.

So at that point, you should actually trust your hiring criteria and compensate weasels with no regard for their color.

(It's true that red weasels are likely to, at one or two times in their career, need a couple of months off for frenzied weasel dancing. But it's also true that blue weasels are more likely to get trodden on by a cow and need medical leave, because they're less careful when walking through pastures on the way to work.)