Interesting question. Over the years, I have had snakes in rooms that corresponded to daylight/dark, rooms that were mostly light (not bright), and rooms that were mostly dark (not always pitch dark).
Presently, my snakes are in my very large bathroom (separate room from the shower/tub part,...that I can easily control temp and humidity), were I have a 25 or 40 watt nightlight on 24/7...just so I don't have to flick the overhead light on and off over the course of the day and night (I am a night owl).
During the day, and post-feeding periods, the corns are mostly in their hides. At night they are usually out, watching me.
I have heard senior members talk about corns becoming accustomed to their tub/viv, to the extent that their whole tub/viv is to them their hide.
I think that having plenty of hiding places to seek and find darkness in their tubs/vivs would be the key thing...for them to have a choice.
Corn snakes in the wild are classified as crepuscular (as opposed to diurnal or nocturnal), meaning most active at dawn and dusk. Hiding out during daylight hours under debris, underground, or similarly concealed.