Clear
I'm assuming you are thinking a clearcoat paint???
It will yellow over time!! Even if you have it powdercoated with a clear powdercoat it will still yellow but last longer than the paint. All depends on how clean you keep it if it's a DD or just toy how much constant heat it sees.
The longest lasting option is blasting it polishing it out and have it powdercoated clear. That's what I am having done to mine but my truck hasnt seen but 30k miles in the last 6 years.