This is similar to another request, except that the icon color/change would not depend on object title naming conventions. In a publication in SDL Publication Manager 12.0.4, you can display a the "where used" window, but you have to click and check each object--the information is available, but hidden.
Most of us work in a publication. It's all to easy to go down the list of topics in pub as you incorporate SME comments or make updates, but totally miss that an object is shared with another map. It would be really great if the icon were different for shared objects (such as a little S partially superimposed), just to give you the warning that it's reused somewhere (and you should check where...).