As mentioned yellow headlights are used in racing series to differentiate a second class of cars running at the same time. What hasn't been mentioned is that the yellow lights are given to the SLOWER class.

If you've ever watched SuperGT (where the fad trickles down from to JDM then USDM) I can't help but think about the faster GT500 cars strobing their white lights at the GT300 cars (running yellow) to communicate "move bitch get out the way."

Slower, not slow. At least in ALMS. Those slower cars are still beasts, they're just not the absolute monsters the big boys are.