You could try this.
I've got a white one and i've just painted a couple of bits on it so the rest of the car stood out a mile. So i buffed the rest of the car and what a difference.
The trouble with white is there's loads of different shades so if it's been painted it might not have been a perfect match.
I really struggled with mine, sometimes if you look really closly you can see a slight difference.
Try the G3 though on the rest but you'll prob end up doing the rest of the car like me.