No, the backlight key(s) of the keyboard will not work when it is not paired to a host device. The backlighting feature on most keyboards is typically controlled through software or hardware settings on the host device, and it requires communication between the keyboard and the host device to function properly. When the keyboard is not paired or connected to a host device, it lacks the necessary communication channel to control the backlighting, so the backlight key(s) will have no effect.