TLDR: When searching for "palette" in the reference it would be a quality-of-life improvement to be able to see an example for each available palette online.
This is the page: https://root.cern/doc/master/palettes_8C.html
This page is what comes up as the only result when one searches for "palette" in the online reference search box. The file is a script to generate a png for each supported palette.
This would be an excellent place to also put an example of every available palette. I imagine it would be similar to the matplotlib dito: https://matplotlib.org/users/colormaps.html
I would request two kinds examples (used where appropriate): one with multiple lines drawn; one with continuous shading (already present on page).