That's supposed to fit with the recurrent theme in the cartoon of the Tasmanian island being all yellowish. I think that aspect it's actually a little more faithful in this game that what the Mega Drive game does in that regard.
Escape from Mars on the Master System is just a straight TecToy conversion of the Game Gear Escape from Mars game, which is of course a better game than the horrid Game Gear Taz-Mania game (I don't get how Sega could let that crappy abomination to happen), but worse and sluggish gameplay wise compared with the Master System Taz-Mania game. It's also more close to the Mega Drive Escape from Mars original than this Master System version is to the Mega Drive Taz-Mania.

