Janet and Alasse, agree it's VERY er, nuanced!
IIRC each season has core colors and then it radiates from there -- I know hair and eye color do matter unlike, say, in Sci/Art. It may be one where some palettes are for seasons that "flow" into one another, hence overlapping colors between seasons.
I should recall more but after a while stuff blends together, ha.
[The system's been around for several decades and I think just got bought up by Color Me Beautiful.]