Currently, View Reps are used to control both colors (a.k.a. "Appearances") as well as visibility. This can be a real pain when you want to use the same color scheme across multiple visibility sets, or show the same visibility set with different color schemes. It's very difficult, if not impossible, to keep a desired color scheme or visibility set in sync between multiple View Reps.
I propose we should be able to create color schemes and visibility sets separately, and then combine them as needed for use in parent Assemblies, Presentations, and Drawings. Perhaps View Reps could be used to make predefined combinations of these elements (essentially, just like they do now). But with these elements separated, we would have the power to configure them individually, and create any combination of them that is needed.