Update `.plotting` to match published styles

[deppen8]

In preparing publications, I used a standard set of colors. We should adopt these (or some other palette) as an official palette across prospect.

Colors from ColorBrewer2 "12-class Paired" qualitative

AREA_LT_BLUE = "#a6cee3"
COVERAGE_BLUE = "#1f78b4"
LAYER_GREEN = {"facecolor": "#33a02c", "edgecolor": "#b2df8a"}
LAYER_ORANGE = {"facecolor": "#ff7f00", "edgecolor": "#fdbf6f"}
LAYER_PURPLE = {"facecolor": "#6a3d9a", "edgecolor": "#cab2d6"}
LAYER_BROWN = {"facecolor": "#b15928", "edgecolor": "#ffff99"}
LAYER_RED = {"facecolor": "#e31a1c", "edgecolor": "#fb9a99"}