Commercial vehicles came rock moss green standard from the factory, but because they were commercials the customer could paint them any color they desired. The choices are open for you.
You have an early '30 eyebrow fender on your drivers side. If you have another correct 31 fender I suggest you swap that one out and put it in a safe place. They are much harder to find than the final production fenders, and therefore worth more. Since your truck looks like a late 31, with indented firewall and wide box, the correct fender will make the vehicle more valuable as well. Welled fenders were available for either side (or both sides, for that matter). You could put dual side mounts on it, which I have on my pickup, and I think they look purty darn neat.