I'm trying to understand-- You have a coop that the chickens go into at dusk for roosting, right? Do they get in via a small 'pop' door just for chickens, or another way?
If it's just the pop door, the owls are very unlikely (not impossible, but very unlikely) to try and get in to mess with your birds, and they should be okay until you can get home and close the door.
If it's a large door, say a people-sized door, you might have a bigger risk of a bold owl flying in for a meal.
As far as I know, red lights will not deter owls.
Really, I would be more afraid of other predators coming into your coop if the door is left open. An owl might take a single bird, but a raccoon, possum, fox (etc) could wipe out a lot of birds in one night!! Even though you haven't seen them yet, I can tell you with certainty, that it is only a matter of time.
Have you considered an auto-door on a timer? They can be a bit spendy (around $100 or more depending on what you need) but I can tell you that mine has saved me more than $100 in lost birds/peace of mind for when I am not home to close the coop up.
Good luck, either way!