Paint Woes
The reason that the yellow color fades, and you get "yellow" on your applicator is due to the physical colorant itself used in manufacturing the paint, yellow oxide. The same occurs with red paint as well, with the iron oxide. These colorants, used in both red, and yellow paints are not very resilient to UV. They break down under UV over time and fail completely, thus giving you the "yellow" on your applicator when you are polishing the paint surface. The fact that the clear coat is actually mixed in with the paint also does not help, as it does not provide a physical barrier between your paint and the elements. Two stage paint jobs, ie: paint, and then clearcoat provide much greater protection but also cost more money for auto manufacturers to do, as it requires twice as many processes.
My P5 is white, and my fiance has a red 1992 Miata, and I use Mothers 3 steps (
http://www.mothers.com/products/productcatalog/paintprod.html) on her car every few months and always get "red stuff" on my applicator. Phase 1: Pre Wax Cleaner - this step removes old wax, and oxidization(yellow or red stuff) from the paint surface as well as other contaminants. Phase 2 - Sealer and Glaze nurtures your paint is supposed to hide swirl marks, but we all know nothing totally does this. Phase 3 : Carnauba Wax - a non abrasive that will add the shine, and radiance back to the surface.
Meguiars also offers a similar system, and I have tried both and they are comparable. I always use Mothers because I find it is a bit easier to remove, but hey that could just be me.
Just my 2 cents!