To the best of my knowledge, there are no "official" urban camo colors (I have never seen any items made out of urban camo colors that have an FSN - Federal Stock Number). Most civilian police SWAT or Reaction teams wear Black (preferred), Dark blue or Woodland Camo. Military Special Operations Teams (SEALS, Green Berets etc) usually wear what ever the mission and area of operation requires (Black, Woodland, Desert, Arctic or civilian clothing of the locals)
I think if you research it, the popularity of "Urban Camo" started amongst college students and was offered as an alternate to the black, brown and greens of woodland camo. No matter how anti-war and/or anti-military college students may be, they tend to buy up a lot of camo items. Its cheap (I guarantee you that you can buy two, maybe three pairs of good BDU pants in a surplus store for the price of one pair of Levi 501s) and they wear well. The first sets of Urban Camo I ever saw were worn by college students. (now you can find them in bright greens, reds, blues and yellows)
By the way, I forgot to welcome you to the Forum. Hope you enjoy it here (Just remember that you don't have to be crazy to be here, but it sure helps at times - hehehe)