While riding the escalator at Rush University hospital and in several other places, while looking down at the moving steps I saw a bright, yellow-green light shining underneath, a color similar to that you sometimes see in copiers while they’re operating. What is that? does it serve a special purpose? And why that color? I’ve edefinitely seen it on several other escalators so it can’t be something unique.
Escalator trolls… 
Seriously, here is Cecil’s answer to that question
Wow, and here I thought I was the only one who asked! thanks!!! Interesting that the guy who posed the original question almost 18 years ago (goodness!!) is also from the Chicago area.