I am pretty sure that there's at least one other game like this out there, or it was at least planned, because unless I dreamed it, I saw coverage/commercials of that game in the early 2000 I think.
It was about covering a city in paint as fast as possible. Not sure if it had a multiplayer or not. I also don't know what system/s it came out for. But when Splatoon was revealed I remember thinking, 'Oh, so it's like that game from way back then!'