New York (Primarily New York City) is the culprit behind the ban on certain kinds of plastic toy guns. The city tried to also ban all toy guns as well. I believe that measure failed, but the toy gun restrictions remain in effect. And since their the largest city in the United States, everyone else gets the same kinds of plastic.
The rules are...
Toy guns must be White, Bright Red, Bright Yellow, Bright Green, Bright Blue, Bright Pink, Bright Purple, or completely translucent. It cannot have a laser pointer (Oh darn!) and the barrel must be closed and the manufacturer's name must be stamped on the gun.
In 1999, the New York City Council expanded and amended the 1955 law
requiring that toy guns be colored white, bright red, bright orange, bright
yellow, bright green, bright blue, bright pink or bright purple, or
constructed entirely of transparent or translucent materials.
In
addition, the toy gun cannot have a laser pointer, its barrel must be
closed and the toy gun itself must be stamped with the name or brand of
the manufacturer.
I'm pretty sure all this law managed to do was cause crooks to get real guns instead. But there you have it. Video gaming (And cap guns) would never be the same after 1988.