Is the light software controllable? Does it come with its own app for that? I've not ever seen one like that, but maybe it's possible.
Without an app to control it, then automator control seems unlikely.
A USB device like a light would just get 5V power from the USB bus. I expect there's no way to software control the USB power without shutting off the USB bus entirely. The light simply comes on when you plug it in, and off when you remove it.