It's interesting that you bring that up Eric. My favorite picture of all time for the effectiveness of camo is the 109 over N. Africa. When you see that scheme out of context, it seems bizarre. When you see it in the environment, the plane disappears.
Always hard to say why schemes are used. Lots of different factors...are they trying to hide from air or ground observation, are they trying to defeat aiming, are they trying to hide numbers, etc.
My father is retired US Army and he's got a great story about his time at Ft. Polk when they were conducting studies for effective camo patterns. The most effective scheme they came up with involved a muted black-and-yellow checkerboard scheme.
Of course, it was never adopted but one always wonders...