I haven't done a tail lamp, but I restored a headlamp kens using a kit, which turns out to be three progressively finer grits of very fine sandpaper, followed by an abrasive polish. This should work, but only on smooth surfaces. I would not expect the colour to be an issue, since it is throughout the plastic.
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
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