Yeah, there might be a way to make it work by fiddling with color values. Green next to blue can be tough, but it’s not impossible. The trick will be finding a green and blue that are also complimentary and don’t create a pallet that looks like a McDonald’s ball pit.
If you’re new to color theory, do a Google search for color theory / color pallet tools. There are a lot of good ones out there. Adobe has a nice free one.
You might also be able to represent land another way. Like using a shape or illustration instead or color.
That said, as someone who’s been doing this for few decades now and directs some design teams, my advice is to keep symbolism to like 2 or 3 things. One you go over that, it can really be easy to get messy harder to pull off. Just my 2¢.
That said, I like where you’re going with this. Will this be officially adopted by the area?