Vectrex Overlay as a Shader?

[cafarellidigital]

I'd like to do something unique (I think) with overlays and shaders for the Vectrex emulator (but this method could be applied to any emulator). I have a little knowledge about basic coding, but absolutely no experience with cg/glsl shaders, which is why I need your help.

The original Vectrex system came with transparent overlays for each game (like the ones used on an overhead projector). Since the Vectrex screen was black and white, these overlays added color. You can kind of replicate this using basic overlays in retroarch (which I've already done), but it's not great.

I'd like to see if there's a way to use an image (in this case the overlay) to "colorize" the white lines of the Vectrex display. On top of that, I'd also like to give the lines a glow. I've attached an image of what I'm talking about, and you can also see an example of the real thing here:

I'm running RetroPie 3.6 (from the SD Card image) on a Raspberry Pi 3. Is anything like this possible? If so, how would I go about doing it? Thank you!