Normally, one doesn't "renovate" roofing felt anymore. Since the 1950s, only asphalt (bitumen) felt has been used, and there is no way to replace what disappears from it. I've never heard of anyone painting it for aesthetic reasons, and what some manufacturers claim about being able to paint it as protection/maintenance doesn't hold up to their promises and usually provides little effect per money spent compared to just replacing it with new felt when the time comes.