It occurred to me that my chosen tempera paints seem to be pairing off. While watercolor or oil painting might have a single color called "raw umber," the egg tempera use of dry pigments mixed with egg yolk allows alternative versions.
I am enjoying having two different raw umbers in the same painting: Cyprus raw umber is warmer, while Italian raw umber is cooler and darker. Or Nicosia green earth is noticeably cooler than Verona green earth. Prussian blue has its own oddball color cast compared to Thalo blue, and together they make for elegant close hues in the same sky. This two-by-two approach could be dubbed "The Noah's Ark Palette."