I realize this is an old thread, but I found it using the Google, which means any newb can too and so BECAUSE it is extremely IMPORTANT that good information is passed on and bad information is stomped out wherever it's found, let's set the record straight ONCE AND FOR ALL!!!
First off, Keefers26 is an idiot (sorry can't be kind to people who talk out their ass as if they KNOW something is factual, when to the contrary ALL the evidence and existing science state otherwise). He and others who constantly say they "believe X is true", but based on nothing more than their own uninformed opinions (and without even bothering to use the Google to fact check their beliefs) are usually the source of SOOO much misinformation, it's sad AND misleading to those who don't know any better. Alright, now down to the nitty gritty,
QUESTION: CAN YOU USE A GREEN LIGHT IN YOUR GROW ROOM AT NIGHT?
ANSWER: YES. PERIOD, END OF REPORT!
Now I could go into all the science, but this is KNOWN information that any experienced horticulturist or botanist can tell you, and it's already been shared in this post by Prot3us1 here:
https://www.rollitup.org/t/green-light-in-grow-room.11892/page-2#post-3892425
But the jist is this: CANNABIS PLANTS DO NOT USE LIGHT IN THE GREEN WAVELENGTH/SPECTRUM. NONE. NADA. ZILCH. This means that it is 100% okay to use a green light in your grow room during the dark periods without fear of doing any harm. And to refute TooRare2Die's statement, NO IT DOES NOT MATTER if you use green LED, or green CFL or a green painted incandescent bulb, AS LONG AS THE LIGHT EMITTED IS GREEN THAT IS WHAT IS IMPORTANT. That the light behind the dye or paint is white DOES NOT MATTER, only what color is projected. However that said, the danger with a painted bulb is that some are not painted well and may be too thinly painted (especially near the socket end) and any scratch is going to create a leak of white light that may be too insignificant for you to see, but the plants will, so LED's definitely have that advantage.
And to reiterate, a cannabis plant APPEARS green to the human eye EXACTLY because it is reflecting light in the green spectrum while absorbing all the others in the visible spectrum of light. This reflection indicates that the plants are NOT using this wavelength so in essence green light is INVISIBLE to cannabis plants. This also explains why we see colors. For instance blue dye isn't actually blue - a particular blue dye simply reflects all the blue light (whatever shade it is) that is within the full spectrum of the lighting available, which is why under HPS lighting, with it's limited red-shifted spectrum, your blue shirt doesn't look so blue ;?D
And let's dispel a few more myths while we're at it. CANNABIS PLANTS ARE NOT HUMANS, so we should try not to anthropomorphize them by saying things like "sleeping" or "waking" or "disturbing" them. While it may be convenient to use these terms, it can lead to some incorrect thinking as to how plants actually grow and function.
It is perfectly okay to work on your plants during the dark period as well, and sometimes absolutely necessary or preferred. This includes applying foliar treatments, trimming leaves, killing pests, what have you, and if, like myself, you have ever had to work a swing shift, there may be days or weeks when it's the only time you can get anything done. So don't worry, be happy, and use green lights whenever you need to to work on your girls (lol, alright a little bit of humanizing our green friends is fine, including giving them plenty of TLC ;?).