It's looking good so far, and I think the grass is fine in my opinion.
However I think that the colors need a little fixing.
Remember: contrast! You have good contrast here, but there are two colors that look almost alike! If you replace them with one color, that will lower the color count, and that's a good thing.
Another thing, more hue shifting! Don't be afraid to try out completely different colors, because remember, you can always change them!
Here's a little edit of mine (I put some AA on the tree to see how it looks):