Yours is most likely the anodized finish if it needs re-doing. Aluminum alloy grip frames and ejector housings have been powder coated instead of anodized for several years now which is much more durable. And the semi gloss finish matches the rest of the blued gun much better.
Since you want to refinish it, not polish it, your easiest option and likely the cheapest is to just buy a new XR3-RED size grip frame from Ruger if you have a New Model.
Since the alloy grip frames are not fitted to each gun, they come already finished i.e., powder coated. You can also check ebay and gunbroker for a nice used one.
For more money, about $40, you can buy a spray can of Cerakote. Push the button in the bottom of the can to activate and you have about 2 hrs to finish spraying. No stripping needed, just degrease.