Better colormap for Effective QC Map Plots

## Description

I think the current colormap for Effective QC map plots is viridis, but I feel they would be better served by a qualitative colormap (e.g. tab20) that is discrete and non-sequential, since QC flags are discrete, non-sequential numbers. As things stand, it is hard to tell whether a particular shade of green represents a 13 or 14, for example.
