Zemmels review: add color-blind friendly plot option to plot_duration_hydrograph

Reviewer asked whether the default color scheme for this function was color-blind friendly. The simple answer is no, however upon discussion, it made sense to make it easier for users to plot with a color-blind friendly option. We will:

• somehow update the colors argument to accept 'colorblind' as a color option, and hard-code the blue-brown colors (as used in the utils.py script) into the function.
• determine how best to add this functionality, as it may require additional tweaks to the function.
• update documentation and examples accordingly.

We have changed the plot_duration_hydrograph function to accept a 'color_palette' input that defaults to the more colorblind friendly 'BrownBlue' palette, but also accepts the original 'Rainbow' palette, or a custom list of colors. Elise notes that in some of her research on colorblind friendly palettes, the 'BrownBlue' is 100% better than the 'Rainbow', but it still could probably be better.

See:

Colorblind Safe Color Schemes (ucsb.edu)

Palette checker - Are My Colours Accessible (aremycolorsaccessible.com)