There was a Mario Party on the GBA? Wait, no. Focus on the art. Ahem, how come... these two... were not featured in the Mario Party on the GBA that I didn't know about until now? Why even have time machines if we're not using them for reasons like this?!
It is perfect as is. Kind of impressive that you have such a relatively clean-looking image from a scanner. Instead of adding color, use that time to continue enjoying your Switch (1 at least) until the next one arrives with a new Splatoon (maybe), or revisit the GBA. Did you know there's Mario Party on that? I didn't until today!