I think, when it comes to the activity, it would be important to have your mockup or revamp work well with the original grey value scale of the gameboy, then perhaps some research could be done into what palettes were used and available, then you could attempt making your piece work in color too ( it seems that hues would change by location mostly. Each pokemon also seems to have it's own palette!)
edit: pokemans have been added. I'm also interested in exactly how the fonts work as the text doesn't always align to tiles, and if I'm not mistaken I've seen at least one gbc game with AAed text... I think?