I have file with several thousand rows, and would like to average one of the
columns based on a second rows groupings. What would be the best way to do
that? Thank you.

Example: (I would like to average all the yellows and all the blues and all
the greens, etc.)

Column A Column B
Yellow 1.34
Yellow 8.2
Yellow 6.11
Blue 7.78
Blue 9.27
Blue 15.7
Green 3.5
Green 1.97
Green 6.55