I think you've done a really good job! I always find it difficult to comment on colouring...first of all, colours can look very different from one screen to the next, and often it's also a matter of personal taste. But I think you've achieved a very successful result for the style you're going for, and the shadows all seem to make sense based on where the source of light comes from.
If I were to nitpick, I would agree with what's already been mentioned - try to avoid tangents. And perhaps draw just a few more bumps and lines on the part of the ground that you've left "untouched" - no need for tons of details, just a little bit. I think all in all you've balanced the amount of detail and "cleanness" very well. I'd just like to see a little more variation in the front where there is just a lot of brown, flat ground, especially since it's next to the grass that you've also kept rather flat in colour and with limited detail (which I think works well).
Anyway! Awesome! Good job
I read the description for the comic, but saw you haven't started posting much yet, so I don't know what it's really all about, but I like this page! With this kind of naked landscape, it has a sort of lonely feeling to it, but the colour of the sky has a pretty optimistic blue I think, so I feel like there's some hope there.