A tautology would be to say my black rims are black, but in this case he described one object as having two mutually exclusive properties. So I guess I was looking for pretty much the opposite of "tautology".
Regardless of misusing the word "tautology", my point remains: saying "my black rims are any colour" is no more correct than saying "my blue car is pink" or "that dry towel is wet".
Well thanks for that