There are a few options for aluminum ribs.
Teflon coat--The color would be the same as a matte blued or teflon bbl. The coating is only about .0005" to .001" in thickness, but very durable against wear and always remains black. It doesn't fade to a dark blue.
Paint--I'd recommend a spray can, not a brush or roller. (I don't recommend paint. Too thick and can chip off.)
Anodize--Is probably what is on the rib now. It's also found on almost anything aluminum.
Anodize with a clear hardcoat--Kolar uses the anodizing with the hard coat. This is probably the best. To do an individual rib is costly. The company I use has a minimum. So with quantities that Kolar has, the price is manageable. The hardcoating is about as hard as a file.
Though I'm not too familiar with CereKote, what I've read is that it's applied the same and is somewhat similar to the teflon coating. The difference is the replacement of a small quantity of ceramic instead of Dupont's Teflon.
The company I use for the teflon coating does a lot of industrial applications, but also for some of the firearms manufacturers here in the states...Weatherby and Kimber, to mention a couple.
Now with that all being said, I spoke with the chemical company that made Remington's Rem-Oil, several years ago. I ask him how much of a particular additive must be in a product for a company to claim it in ads and on the product's can. He told me one-tenth of one percent. The company I use, and I'm sure CereKote, if asked, would not tell you their propriortory secrets.
Speaking with my coating salesman, they now have a procedure for doing bores. He has done his sporting clays gun and says it's holding up well. I may try this out on my 90-T and shoot it through the summer to see for my self. It may help with the plastic melting to the ID and being a bugger to scrub out.
Going back to the Rem-oil deal real quick, the chemical fella also said that any liquid with teflon in it has a shelf life of only one month. The teflon settles out and sticks to the bottom of the can, and becomes useless.
Oh, just call me Doug, I don't wear a tie to work.
Doug