FG: Add pallet options in figure elements.

[john-harrold]

Include options for color blindness as well as some other options for variety.

          For the palette, this page suggests blue/red as the pair to use.  Maybe add black as the "other" group, too.  (https://www.datylon.com/blog/data-visualization-for-colorblind-readers#color-blind-palette)

For the graphs, I would lean toward making color selection and advanced setting that applies to everything rather than a per-graph option.

Originally posted by @billdenney in #17 (comment)