beats me... it just happened... they were APC lights, i looked on the site and it said they were for chevy, but at the store they said universal... but before i found that out, i poped them in and turned on the parking lights and blew a fuse, then i replaced the fuse and stepped on the brake and heard another pop/crackle, but it wasnt the fuse that time.(and i checked both fuses)
well either way i filed a claim at the store, but the store said the claim will be against the company, not them. so they filed it for me.
oh and as for the signals turning yellow... may take a while, but i wouldnt doubt that it wont happen, carbon build-up happens to most headlights, there are ways of fixing it, but its all up to you which you choose to fix it.