White color is often achieved by the addition of TiO2, Titanium Dioxide, which is, essentially, titanium rust. Exposure to ultraviolet light will attack the binding resin, in this case the polymer base.

That will bring the titanium dioxide directly to the surface, which will begin dulling whatever gloss it had, and begin giving it a chaulky appearance and feel, sometimes coming off on your hands or whatever it contacts. As time progresses it will begin crumbling apart as the binding resin deteriorates.

Try a blue or red chip. These are colors in which the pigment are not as stable as the titanium dioxide. As soon as the binder starts deteriorating from the UV, if the pigment used are organic pigments, they will begin to fade.

If the manufacturer of the chip used ceramic pigments the color will maintain its original hue for a much longer time, but the resin binder will begin to deteriorate.