After two weeks of testing, I finally selected the darker bow and sent the others back to Cellos2Go
. I'd gone back and forth between it and the lighter colored one from the first day. But something one of the (anonymous) commenters said this morning helped me sort it out: "consider the one that 'sinks' into the string best". That described my first reaction to the dark bow. It not only felt right (as did the light one), but it seemed to be smoother on the strings, drawing a cleaner sound with less apparent effort.
Whew. So now: the cello is in good shape; the bow is new and good quality; the strings are relatively new and seem to be the right match. No more excuses, it's all up to me, now.
Another 45 minutes on the Beethoven Minuet
today. After several pizzicato repetitions, I began using the bow - one segment at at time.