You know i have this theory that involves the seven sins and virtues. Frisk/Chara are diligence going against sloth which is Sans. Im not really sure what to correspond with the others, what do you think they would be?
Toriel is Gluttony, Papyrus is Pride, Undyne is Wrath, Muffet is Greed, Mettaton is Lust, Asgore is Envy, I guess Sans would be Sloth.
The Light Blue SOUL is Temperance, The Orange SOUL is Fortitude, The Dark Blue SOUL is Faith, & the Purple SOUL is Prudence, the Green SOUL is Charity, the Yellow SOUL is Justice (they just don’t change at all). & I guess the Red SOUL would be Hope (because I didn’t see any Diligence in the list that I found).