In the QM's with a courtest car lineup there are weight icons within some of the car select buttons, above the car weight. I've been unable to discern their meaning, any info would be helpful. Looked in the manual to no effect.
Well my favourite of the GT3 cars, the Z4 is 1,190 kg's straight from the dealership, so your first thought: "Weight added to get to the weight displayed?" is correct.
As for the yellow vs. red icons, that one I'm not sure how to answer, but I think it's the differences of the weights themselves... up to 20kg's is Yellow(gold) 30kg's is a not so dark red, 50kg's and above is the darkest red.