There's also a version sold by Eastwood Company. They have a lot of powders available, including high temperature satin black.
The coating can be thick enough to cause problems if you lay it down heavily. Just like spray paints you can go over areas with a little less powder to adjust the thickness, like on the rails.
The Eastwood option is a little more expensive, but it comes with an 8oz can of gloss black.
There are a few other sources for powders that will work with these systems. If you search you may
be able to find something close to gunmetal blue metallic. You may have to mix a couple colors of powder to get the effect but a powdercoated "blued" finish would be incredible looking and durable.
Powdercoating shops may be able to help you find a mix of colors that resembles hot blued steel.