Is there a tool which can ease recognition of similar desktop windows
- by attaching some color mark to them OR
- by re-coloring their window frame
- by other visual means (except of changing title text, which is often small for purpose of distinguishing windows)
It does not necessarily need to be free.
Windows of productivity applications often look nearly the same and you need to read window title or part of the document inside to recognize which one you actually see. Possibility of adding some big visual cue would make work in such cases much easier.