There is a difference. I just recently bought 6 from Best Buy(Colorado). They had two in stock and hade to ship to 4 to home. The 2 I brought home had black motors and the other 4 had silver motors(all 4 were shipped from Ohio). The difference is what is inside the packing. Black motors came with:
Black battery w/charger
Black rotor blades
ST10+ Transmitter w/shield
16GB microSD(even though the packing list says 8GB)
AC/DC Adaptor
Motor Holder
CGO Steady Grip
Typhoon RTF Airframe
USB Interface
Now the other 4 were a little bit different. They were the same except for:
8GB microSD
Neck Strap
Tweezers
White Battery
I've hade a few pilot mishaps with the first 2 I purchased (black motors), and the replacement blades I purchased were white. So far there has been zero difference in flight stability and control. The replacement motor/ESC controller I purchased was a silver motor and yet the same results, zero difference in flight stability and control. So far there has been no difference in flight stability and control between the 6 Q500 4k drones that I purchased. Also all firmware was current with 1.07 version for all drones.