These are the 3 people living in the Kochi Dye Shop in Hateno: Sayge (the shop owner), his wife Senna and their son Sefaro.
The leaves of the Senna Tree, Saffron and Common Sage are all used as seasoning, but they can also be used as natural dye materials, and they all yield different shades of yellow. Saffron dyes cloth in a rich, golden yellow, whereas sage yields a green-ish tint and senna yields a slightly more orange shade.
I have no idea if that was really the intention behind their names, but IF it was the case, then it is a really nice detail that their very names basically stand for 3 adjacent spots on the color palette.
… and it is only one of a myriad of other details, but since Lemmy doesn’t support video format (yet) I’ll have to link to youtube for that: