it's probably sun fading... my whole truck looks different.. the metal fades at different intervals than the plastic...
check your grill shell, it's fiberglass, the hood is metal and the bumper and side skirts are abs, or poly, or whatever they are, lol... all 3 of those will fade differently... and red is one of the worst, if not the worst color to start fading...
only way to fix it is to repaint it...
you can use flexible filler, so depending on the damage, it may be fixable...
PR4 is expensive paint, so you'll be in it for at least $500 say $250-300 for the bumper and another $200 or so to base and clear it... but it may only cost you an extra $100 to repair the bumper...
post a pic...