Consider changing get_year.py to read color schemes from external TSV file

[kimandrews]

Currently, scripts/get_year.py contains a hardcoded list of color schemes that was manually converted from the ncov color_schemes.tsv format.

This could make maintenance difficult if colors need to be updated.

As discussed, we could move the color definitions to a separate TSV file (e.g., defaults/color_schemes.tsv) and have the script read from that file.