Flashlights most often than not, do not spook deer and there are countless examples and experiences with people seeing a deer within 20-40 yards just standing there curious about the light source. Yellow and White light source do however get their attention.
Hunters recommend that you use green or red light to hunt as it does not interfere with your night-vision and deers do not see them that well. You will still be able to see quite well and for game besides deer, green and red light do not spook other types of animals as much.
Can I Not Use a Flashlight?
If you like hunting in complete darkness, it does increase your chances of being accidentally shot by other people who are hunting. They might mistake you for an animal and shoot you. There are many accidents like that, so it is better to hunt with a flashlight so other people can identify you.
Someone commented On the the thread: https://forums.bowsite.com/tf/regional/thread.cfm?threadid=242542&messages=23&state=ma
“deez…I had a buddy & fellow trad bowhunter setting up his climber at the base of a tree in a clump of small pines get shot in the dark by a rifle hunter in NY. guy heard the rustling in the brush and ‘thought it was a deer’. luckily for my buddy the bullet didn’t hit any major arteries or organs, and the guy at least called 911 and stuck around. this was probably 15 years ago. ever since then its flashlight in the dark or if I’m going in midday some piece of orange that I take off once in stand.”