I don't believe brake pads or rotors have any bearing on the ABS light or system. I thought I had a photo of the wiring diagram for the brake pressure switch but can't lay my hand on it at the moment. If memory serves, the red and amber light switching in the pressure switch act pretty much like the two sides of the same relay, one normally closed (red) and the other side (amber)is normally open. That part is independent of the actual pressure switch that controls the pump. The operating pressure is between 2000psi and 2650psi, the lights trigger off somewhere around 1700psi and trigger on at around 1500. You can see that effect when the key is turned on after sitting for a while. Assuming the ABS is otherwise sound, when the pump is running pressurizing the accumulator, the red and amber will be on but when the system reaches the trigger point above, the lights were go off pretty much at the same time. There may be a slight lag on one or the other, but relatively simultaneous. My pump and accumulator test rig has lights connected to check the pressure switch functionality in all phases so the amber light can be triggered through the pressure switch as well. I have never seen a bad one, but I would think it could be checked with a VOM to see if the amber light is because of a defect in the pressure switch. Sorta spitballing here.
Edit: I believe the reason for the open switch on the amber light is when it trips, the switch closes and sends power or some indication to the ECBM that the pressure is sufficient.