HK? seriously HK has enough weapons for three-tier upgrades last time I checked.
its hard to filter through the kinds of weapons but once you do there's like 5 different SMGs, 4 different snipers (and 2 that could be called snipers but fire relatively fast semiauto), 3 LMG's, a multitude of automatic assault rifles and semiauto rifles, 2 burstfire guns, 3 pistols, ~3 machine pistols?, and 2 revolvers.
As for color, they're not all boring grey (most still use grey but there's browns and greens) and they have distinct model shapes that allow people to identify what they're up against
I don't really see the point of iron sights. It just forces people to click one extra button before firing.