I dug out a GM I made ages ago (probably over 20 years ago).
I painted it with desert yellow from a spray can, and added grated pastel powder for the brown and green, spreading it on and spreading it out...and then set it with a matte clear coat. It was a three-color camouflage that didn't even require an airbrush! That was back then, and I was trying my best.
It's a little difficult to recover if you make a mistake, but it's easy, so I might give it another go... (Well, I have an airbrush now...)
This regular GM turned out surprisingly well.
(；´・ω・)

Just go to the gym | しのっぴ's Gunpla works