I did a project that ended with surplus: an 18ft pallet and 3/4G of exterior premium weatherproof white primer. So, of course, I painted the pallet with the weatherproof paint and I'm going to have it upright with cables holding it to a tree and it's going to be a climbing toy for my kids. But then I realized a white thing like that wouldn't look very nice among trees. So I'm looking for a color that would make it just blend in with the trees. I've already primed it white so I cannot go back on that but this is premium weatherproof BM primer so it's already weatherproof. So this coat is primarily for aesthetics. Even if it peeled a little that would be OK. I just want to aesthetically blend it into the trees. I'm not looking to really paint tree bark textures or anything fancy. Just one color that blends in.
Given the question's added single color requirement: Light brown is probably the best all year round color. White would blend best in winter, but a green in summer; brown is typically seen year round. You can go to pretty much any home improvement store and take home sample swatches of various browns to compare to your trees if you want as close as a match as possible for blending.
The original question didn't specify a single color and this was the answer I posted.
What about camouflage?
A variety (4 or 5 different shades) of greens and browns will work well; maybe it could be a weekend project for the family.
You simply draw irregular blobs on cardboard and cut out the blob for the remainder to be a stencil you will use to spray paint the object.