C2MS — use of color is discouraged

For all message diagrams, color is problematic. Make black/white for printing, copying, etc.

lighten front 3 images and make all message diagram color lighter; also, remove table row header colors

Spoke with Jason Smith at recent meetings (either Seattle or Ottawa) and he said this is not a show-stopper. I propose we meet in the middle and I lighten the color so that there is still some color for aesthetics but printing in black/white shows up better (and uses less ink/toner).