I think I may have worked out a way to get 'infinite' paint chips - it looks like if you are gifted a motor vehicle, you automatically have the paint chip for this when you get the car - I'll have to test that, but it might be when there exists a colour you prefer, you just have to find a friend who has a car with that colour, make sure he can gift it to you, then just gift it back once you grab it from delivery and have the chip.