The pad will only have paint colour on it if the car is painted in solid colour!
Most newer cars are clear over base so if you then start to get colour on your pad its time to worry!

G3 is very harsh so would be extreamly carefull using it.. but if you do use it..

1st most important thing to do is WASH THE CAR thoroughly!

Keep the panel wet/damp
Try and stay away from edges
Only use a couple of pea size blobs on the pad
Work 2ft x 2ft areas at a time
Start with a slow speed - slowly working up
Refinish with a finer compound polish
Apply a wax/sealer