Yup!
Blue base coats are more prone to UV damage(UV rays will penetrate the clear's UV blockers), over time, the surrounding areas of the paint/color, will be "faded" out in the blue base coat., so the base coat and clear under and the "decal" were not subjected to the UV damage.(IE-fading of the pigment of the blue base coat). Buffing and polishing do not replace the lose of pigment.
Black is another issue, and that is as always, a crap shoot.
Black pigment will vary depending on the paint manufacturer, some use more "brown", some more "orange/red", etc, in the creation of the "black",and each of these base coats, depending on the "resin" content of the base material will react differently to UV exporsure.
I know it sounds complicated and it is, sorry, just the facts.
Grumpy