Question: Why is YOUR insurance company handling this? Was the person who hit you uninsured?

I've seen ads on TV recently for legal firms that specialize in civil suits to get compensation for the de-valuation (izzat a word?) after an accident. That may be a better option for you than to keep beating your head against that insurance company's brick wall

If you are going to keep going after your insurance company to make it right, a better arguement would be to have them professionally match the faded cladding to the new. If they won't do that then you will absolutely have grounds to take them to court for compensation.