If you could sell naked parts separately like battery, mainboard, screen, touchscreen - without glass then people would be able to insert it into their own custom cases, attach to their own glass, etc.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I think it's going to be super tricky to try and change it yourself as has already been mentioned, so vinyl/paint is probably the best bet.
However you can buy replacement screens from us for not that much money: https://shop.espruino.com/banglejs2-lcd
So you're welcome to buy one and see what you can do. If you break it (which is quite likely!) then it's not like you've lost that much.