I'm believing that the cheap non-UV stabilized ABS Plastic, which it seems all Cheap Chinese BMW Emblems are made, is NOT UV RESISTANT. The Cheap Chinese emblem white section I had for the steering wheel yellowed just like the one in your picture. A quick Google search (after the fact) reveals that ABS is bound to fail. Sorry for sentence structure but you get the idea
But do your investigation
https://www.google.com/search?q=is+a...hrome&ie=UTF-8