How can I go in my grow room when the lights are off to foliar feed if I cannot turn on the light?

Answer: I would not recommend going into a grow room when the lights are off, however if you most go in when it is supposed to be dark I would use a green light. According to George Van Patton in his book entitled Gardening Indoors -

"The smart way to visit a garden room during the dark period is to illuminate with a green light. Short-day plants do not respond to the green portion of the light spectrum."