I to have the same problems with RBG visuals. I edited bumblebee.conf, the default value was proxy, so I tried rbg and xv and a couple other but still got the same error mesage

$ optirun glxspheres
Polygons in scene: 62464
ERROR (593): Could not obtain RGB visual with requested properties

Thanks for the great writeup. In sudo start bumblebeed ( you did drop an e.) I had to go through your example twice to get it right, my own fault…