I got this idea from my current project.
We have several apps running in the same server, with different layouts and color schemes (this could even be a development server, which is probably the best example) and I got this issue with the color of the popup editor bar on top.
First with every update you do with core eSpaces (such as EnterpriseManager/Enterprise) who may carry a new version of the RichWidgets eSpace, will revert the color of the bar to the original blue, making so that we need to edit the eSpace everytime there is a new version (which per se isn't a big deal, but with multiple apps running is a bit problematic)
So my idea was to add, in the Web Block Properties (see attached img) for the Popup Editor web block, and optional parameter with color (or CSS style if u really want to improve it a bit further) for the top bar, allowing some more customization of the application
It's a small improvement, but IMO can be a major advantage in development servers or production running multiple apps with different layouts (as is my case atm)