a light switch is 'un interrupteur' (masc.) or familiarly 'le bouton'
well most people say turn off the light but you could say switch of the light.
To say "light" as in a light color in French, you can use the word "clair."
Commutateur sur l'as.
a light skin (in the sense of "fair complexion") is 'peau claire' in French.
In French, "light blue" is translated as "bleu clair."
Lampe
leger = light
You say "turn on the light" because that is what you do. Turning on a light means to flip the electric switch from "off" (where there is no electricity and the light is dark) to "on" (where there is electricity and the light is glowing).
The English phrase, "writing with light", is "écrire avec la lumière" in French.
To wire a French light switch, first, ensure the power is turned off at the circuit breaker. Connect the live wire (usually brown) to one terminal of the switch and the wire going to the light fixture (also brown) to the other terminal. The neutral wire (typically blue) should be connected directly to the light fixture, without going through the switch. Finally, secure the switch in its box and restore power to test the installation.
Feu vert
Ampoule - light bulb.