Blue = lights are on or off
Green = Pit line limiter
Yellow = Hazard/indicator lights
Edit: from what i know it is a new feature for the new patch because in patch Z the lights are in a different order but in 0.6A the lights are rearranged to handbrake, Not sure, rev limiter, lights, pit limiter, Hazard/indicator lights.
Edit 2: from what i can tell the xrr has an oil light warning so i am guessing it could be for that.
My uncle likes them too, probobly one of the lightest set of wheels you can buy, and they do suit Mk2 Golfs anyway. Especially diesel ones, where the rear wheels get covered in diesel smog.