How many times have you left the train room light or even your garage/outdoor light on overnight where lights are hidden from view say a garage when door is closed (yes I know there are the "perfect" people who never forget, but this is for the rest of us mortals here)?
With my eyesight, its gets harder to see the train room light switch toggle position from a distance. I considered installing a switch with a separate 110V pilot light (not the type switch that glows in dark when lights are off and hard to see during day).
My simple solution was to paint the underside of the switch toggle when handle is in the up on position, a bright red. When toggle is down paint is hidden. Now I can see the switch from a distance and save steps and electricity and extend light bulb hours..
This idea can work with 3 way switches AS LONG AS the other 3 way switch remains in the position that allows the house switch to function as on/off. Of course if both 3 way switches are used then this idea may not work for you.