Auto rotate – This was a feature available in earlier versions of the app, but I removed it by user request and added the “graph” button for the reasons @ville mentioned.
Graph color – The graphing code underwent an overhaul a few months ago adding some new features – like individual panning and zooming of the channels, and I changed the background color from black to white then. I did not have a scientific reason for doing it (I remember some complaints about the black background being ugly, but you can’t please everybody).
I added a github enhancement to allow graph color selection. I’ll try to get to it soon. Or if you are inspired, the code is open source and I merge changed pretty fast.