Swain's only available in white. It can be painted. They call their exhaust coating "White Lightning" and for some reason they don't like talking about what it really is.
Zircotech is pretty straight forward about their exhaust coatings. http://www.zircotec.com/products-services/for-the-road/exhaust-coatings/
I'm sure there are differences in exact composition and other details.

I have had plasma sprayed headers twice, once Swaintech's and years ago Blackjack's Alumi-coat. Unfortunately in both cases the headers didn't fit right and so don't have personal experience with the performance over time. I'm selling the shorties with the White Lightning so someday someone can tell us. There's no obvious reason why the color would change but the rough surface easily can retain grease and similar dirt.

Properties of TBCs at ST

Blackjack's old "Alumi-Kote" discussed briefly and pictured in Ceramic Coatings Worth It? on FABO.