I've recently purchased the Monster Codex for Pathfinder and found an interesting passage in the introduction to Kobolds. It reads that in rare cases, there are those born with metallic scales that can become great shamans and leaders. However, when looking online for specific racial bonuses for the color, they don't go over what metallic Kobolds do. So is a Metal Kobold a Draconic equivalent to Dohnut Steel, or are there specific racial bonuses given to them?
These racial variants/feats/extras linked below give some ideas you might want to use.
...But there doesn't seem to be a huge amount of concrete rules info on run-of-the-mill evil NPC kobolds with metallic scale colours. It depends how creative you want to be with the bonuses - you could simply give them similar energy resistance bonuses to the Chromatic scale colours (5 vs their own breath energy type), or go for a charisma-related diplomacy type buff.
Of course if you're running the game and you don't mind deviating from what little is written about them, you could houserule in whatever the heck you like as long as your players have fun with it.