Oh, but the backgroud is supposed to be über-detailed forest of lushness, this is simply a placeholder. That the two colours are dark green and some yellowish light green is just to remind me of that the end result I want is a dark lush forest with magical greenish shining-through-leaves-light flowing down below. :]
So don't you worry

Also, I was on the phone while posting the thread so I have a few more things to add;
The big 'hole' thing is supposed to be filled with water, so the background and possibly also the rocks are going to change colour as it goes deeper and the bottom is of course filled with seaweed, bubbles and nice fishies. This is also supposed to be a forest village; Plus that the screen size is supposed to be that of a Nintendo DS so you're not supposed to see this much in the vertical space; When you're up walking on the grass, you will only have a vague idea of what is down under water, and in the beginning of the game, you can't dive very low, so it's supposed to be a kind of secret-in-the-middle-of-a-village-type of thing.
Oh yes, this is a forest side village, so If I'm able, I'll add a house and so. Maybe a nice bridge over the water too.
And coming is a diving main-character and a GUI. :]
Rant over, go on now, you all.