Coloring Automotive Valves

I work for an automotive valve manufacturer. I am looking for a plating/finishing process similar to chrome plating that would give our parts the hardness and wear resistance necessary for proper performance in a gasoline engine, but also enable us to "color" the valve (other than black oxide) in a similar fashion as anodizing does to aluminum. This is expressly to be used for a marketing niche. Valve material is a heat resistant alloy (specs can be given upon request).

Even though the application is for marketing only, I believe the only coating approved for internal engine components is black oxide. If the engine will never be started, then maybe a PVD coating might do the trick, or possibly an e-coat. These are available in many colors.

Hope this helps.