This is sounding great! Anyone thinking about making labels for games that may get the colored cart treatment? Or is it possible to do what youre describing while keeping original label intact?
Painting around labels is crap. People do it all the time and it ALWAYS looks like complete shit. You gotta replace the label if you want it to look decent.
It would be nice to actually get some cartridge shells molded in gold.
Gold plastic isn't really all that swell

The problem is that there really is no such thing as a good pigment which can be used to color the plastic. Instead, a metallic powder/flake must be mixed in which is terribly obvious when you see the results. The best way to see what I mean is by comparing an Ocarina of Time cart with Majora's Mask. OoT has a post-mold finish applied and MM is made with gold plastic.
I wonder how that could be done and what it would cost? Surely making a mold from an existing cart would be fine but finding someone to actually mold it is a different story
Retro USB has an NES cart shell tool in China. You'll prolly have to order a few hundred though in order for it to be worth his time (if he'll even do it for ya).
Well, there are tons of videos on youtube for making molds with silicone for resin. I've researched with the intention of remaking TG-16 jewel cases but I still have yet to do so.
Don't bother. Casting a super thin part like that is very difficult to do without imperfections (I.e. air pockets) plus you'd need a material with a high enough shore hardness to replicate ABS, which won't be cheap.
Casting is HARD, expensive, and time consuming.