But Denti, if you increased N1 on ground, The bright blue lights for Wing Anti Ice go dim! So it is somewhat dependant on N1
You have it backwards, if the thrust levers are advanced on the ground with wing anti ice on , the dim blue lights go bright because the valves are closing and are no longer in the selected position.
The switch/light logic is:
light off-switch off and valve is closed
light dim- switch is on and valve is open
light bright-switch and valve position disagree or valve is in transit.
The wing anti ice valves are electrically activated/driven (as Denti pointed out). When on the ground there are two things that will automatically shutoff the wing anti ice.
Overheat protection via overheat thermal switches in the L/R leading edges. If either switch is triggered at 257°F the valves in both wings will close.
If the thrust levers are advanced, switches in the autothrottle switch pack close and send a signal to close the anti ice valves. This is done to conserve engine power for takeoff.