If I use the selection tool and drag over an area, to select some things, the "canvas" changes a little bit. Everytime I do a new selection, it shows all the previous selected areas drawned.
Like this:

If I change the viewing angle, and select a different object, it shows the same image above.
And here's a screenshot of what happens, while using the selection tool, without the riched20 library:

I'm using version 1.7.9 and Google SketchUp 8. The same happens with the latest version of SketchUp Make (I think 13.0.48).