In an urban setting the only effective camo is no camo.
I have to disagree here. An unpainted gun "looks" like a gun. A gun that has some form of camo on it breaking its outline, doesn't, especially at a little distance.
Ive been painting guns since the 60's, and have always found that the gun thats been camo'ed, is less noticeable (as a gun), regardless the pattern.
As far as an "all around" camo goes, even in an urban environment, Multicam works really well. When it first showed up, the company that developed it, Crye Precision, had a pretty extensive gallery on their website, showing how well it worked in just about any environment you can think of, including urban/suburban environments, with brick, block, concrete, etc., typical city type backgrounds, and it still breaks the outline very well. The pics they had in urban environs were pretty amazing.
One other thing to consider, just wearing a cammie jacket around town, can create its own "background" to hide a painted gun.
Ive actually done just that a couple of times, just to prove the point to a couple of buddies. Even at almost contact distances, just passing by, its not really noticeable, unless youre really looking right at it, and even when you are, your brain isnt screaming "gun".
Anything that confuses the brain, can work.