Sorry, I was unclear.
By "explanation as to what the scene is" I meant graphically. If it were pouring into a river or something, that would show that that nasty green stuff is polluting the river. If there were floaters floating, that would show that it was sewage. As it is, if I ignore the textual description, I see it as some sort of mad scientist lab that mario should be hopping around.
As for the palette, do you plan to change the colours at all, or are you keeping your colour choices?