Tan pants, green shirt or jacket, doesn't look out of place in everyday life, and blends in fairly well into the sonoran desert.
To me though, camouflage is more mindset and tactics than clothing.
Shape
Shine
Silhouette
Shadow
And spacing if in a group.
That and local vegetation or dirt works pretty well. I do generally paint my rifles, especially the parts my body touches, as much for camouflage as to keep it from getting painfully hot in the sun. Getting my cheek burned by a black rifle stock left in the sun was enough to convince me.
I am partial to british DPM though, I like the way it looks, and I think it's pretty effective.