Depending on how deep the coloring is in the anno, you can often bake the color out. I've done it many, many times with aluminum parts of all colors. Try baking the chainring at a high temp (~450º) in a toaster oven for an hour or so. If the anno isn't deep, it will go to clear, if it is, it will end a sort of titanium/gunmetal color. If it ends the titanium color, you can always strip it afterward to get to the bare aluminum. Just know that the bare aluminum surface begins to oxidize immediately, so unless you like dull gray, the polishing process is never ending.