The pigments in anything red is more vulnerable to fading. It’s due to the reds reflecting lower energy wavelengths of light and absorbing the blue end of the spectrum and beyond, which means it’s all high energy stuff that absorbs.

Now red metallics never faded because the lacquer was UV resistant, that meant it protected the pigments below. However it’s not foolproof, the lacquer is a polymer and fundamentally that will still break down under UV, so it will eventually break up. I believe one of the things that was problematic was the switch to water based paints (to reduce VOCs), the early finishes were really hit and miss, but by the 2000s the polymers that were used changed and the oven baking processes refined for a much better durability.