Where this situation occurs on carpeted steps, there are two possible solutions:
- Recarpet the stairs with a two-tone carpet scheme so there is a contrasting color strip for about 2" along the step nose, or
- Add a grit covered metal or fiberglass strip that is screwed-down over the carpet and crushes down the carpet so that the top of the strip is even with the remainder of the carpet so there is not a trip hazard.
The strip color should contrast the carpet color in low light. Our vision tends to loose the color component in low light conditions, so an easy way to test this is to view the proposed color combination with a black and white video camera or still camera that is slightly out-of focus. If all you have is a color camera, then take the picture and pull the color saturation out of it with a photo editor. What may appear to be a good color combination to youthful eyes in full light, may indeed not be a good solution when viewed as an elderly color-blind person.
Other listing of interest: http://theatresafetyblog.blogspot.com/2010/02/tread-lightly.html