This issue stems from the lack of clearcoat.
Almost all modern cars are now clearcoated - until very recently, red Vauxhalls weren't, even the VXR models. I don't know of any new car that doesn't have a clearcoat.
This lack of clearcoat allowed UV penetration of the paint system and, essentially, the sun would bleach the top layer of paint.
Regular waxing or topping up with a sealant with UV protection helped but was always prolonging the inevitable, especially with cars stored outside; garaged cars, not exposed to sunlight so often or for such long periods of time won't fade to near the same extent.
To remove the problem, polishing was/is the only issue; essentially you are removing the uppermost portion of the paint surface, revealing a fresh, red layer underneath.
Other colours, if non clearcoated, would fade but the effect is less pronounced than on red.
The Corsa in the photos above, will, over time, fade again.
Modern clearcoated paints will fade ever so slightly (the sun being so powerful) but it will take a long time for any noticeable change and even then, I doubt they'll ever fade like the old non-clearcoated finishes.
Products such as the Werkstat range offer good UV protection and they'll certainly help prevent the onset of fade.
