Notification for the busiest room in my house

5 people / 1 bathroom
2am, I have to use the restroom, really good chance it's occupied.
Walk across the house only to find the door shut, then I get back in bed.

What's the least offensive light I can have on all day, and night, that shows either red or green. So I just have to look at the light to know if it's available.
I would love something small.

Any suggestions or ideas?

Thank you

aahhh. I could not find this type of night light.
I have a door contact sensor since the door is always open, unless in use, as a house rule.
That light seems perfect. I'll have to try it out.

In the compatibility list, is it the 'Generic Zigbee Outlet' ?