This the the Material Room setup for that camouflage. It's not particularly complicated, just a simple chain. The first Spots shader node does green blotches on a yellow background, and the output is the base colour of the second node (the white setting means the input isn't changed), with brown blotches added. And that goes into the third shader node which adds the small black blotches

If I want desert camouflage, I just change the colours. I prefer the Ctrl-click option on the colour boxes.

Choosing white for some colours is important. It means you don't change the colour coming from the previous node. Or maybe you want to?

Try adjusting the various numeric values in the Spots nodes. See how Spot_Size and Threshold have different effects.