The local high-volume Chevy commercial dealer stocks almost all of their vans and medium-duty trucks in white, since that is the easiest color to paint over.
Kentucky's state fleet has found that buying vehicles with standard color and option packages has lower life-cycle costs, since the manufacturer's don't have to make special production runs, and resale value is much higher.
They used to buy things like stripped AMC Concorde's, but now they get pretty much standard-package family-type sedans such as a Ford Taurus or Honda Accord. I've even seen state Impalas with the LS trimp package, which really shocked me.
Years ago, state transportation department pickups were invariably safety yellow. A friend in the department told me they were amazed at how much more plain white trucks brought at auction. It is impossible to disguise one of the old yellow Dodge pickups, but for some reason, the later white pickups are easier to spiff up.
But the general use state fleets (pickups and cars) come in a variety of colors. Our agency has some metallic silver or tan Chevy Silverado's with nice factory wheels.