The problem is with reds and yellows mainly. Thats why you almost never see true red or yellow house colors. The are always more of a yellow oxide or red oxide. Thats why red cars always fade quicker as well. The additive used in red car paint to keep it from fading is only made by one company in the world. (they have a patent on it) So red and yellow ink that holds up to UV will be very hard to find. Be sure to let everyone know if you do find one that holds up!