Plot Backgrounds on Capabilities Analysis

[k-tatgenhorst]

I submitted an update for ss.ca.r which gives control over the colors. The plots on the left continue to have a white background when the background color is changed. It is not horrible, but not optimal. I believe it is related to using viewport without defining a rectange, so it either needs defined rectangles or perhaps a background can be set in the actual plot.

As this was only a minor aesthetic, I chose to submit as is and address later. If anyone reading this knows, please feel free to tweak it.