I made a new speed indicator plate for my Maho mill, with an approach similar to what you were thinking / PeterT suggested. The original plate had black lines and number on a silver back ground, then colours for different options - in my zeal for cleaning I washed the colour off (the lines were not effected). I had taken pictures first, so I knew what it needed to look like. I scanned the plate, and imported the image into MS paint, then I repaired all the lines, then I "poured" in colour (which in MS paint fills only the bound region). I printed many copies to get the colours as close as possible. Finally I printed onto a sheet of mostly transparent Avery label material. I made a new aluminum plate. The result was great (now I'm thinking the feed indicator plate - that is original - needs to be renewed, it looks sort of shabby!).
The first picture is the plate prior to me "cleaning" it, then the "cleaned" plate, finally pictures of after and before on the machine.