Resetting a Smart Bulb readies it to pair to a Gateway in pairing mode. Here are reset instructions by brand:
To pair a GE Smart Bulb again or pair it with a different Gateway, power the light on and off 5 times in a row at 3-second intervals.
Lightify bulbs follow the same procedure as GE.
Cree bulbs follow the same procedure as GE but only need 4 cycles.
If necessary, repeat the process.
Note: Philips Hue bulbs can only support a one-time pairing. They cannot be reset.