Yeah, that probably makes sense for most situations, especially if the 'color overlay' is a sticker over the VFD, then it's hard to see what the actual color is without trying to peel it off... Might as well just stick with that, probably easier in the long run.
I'm working on Coleco Donkey Kong now... That one has a LOT of vector points all over the place (like 20 or 30 just to make a circle) Since it's mostly a couple of sprites used throughout, I'll fine tune those and just duplicate them all over. I'm curious if the in-MAME SVG renderer will work better with a few thousand less nodes to calculate...