I think it can mean both. For example: if you are throwing a surprise party and the person who is going to have the heart attack when all of you (people at the party) yell at him is about to come in, you can say "hit the lights" and you will be asking for help to turn off the lights for the big surprise !! ... do you need a balloon? O~ here! orrr... if you just finished showing a video with the lights off you may say "can someone hit the lights?" and that would mean "turn them on" :)

這要看情況兒言： 開著燈時說是叫你把燈關燈 關著燈時說時是指把燈開上