I was in elementary school and the library had a book I would read every year because I loved it so much It was a bout a witch who would make potions and I think maybe the potions had the names of colors. Like blue potion and green potion. I think she was also in a school too
Lost Classics of Teen Lit: Name That Book! 
Possibly 0ne or more of Deborah Hautzig’s ‘Little Witch’ books?
LikeLiked by 1 person
“Little Witch” by Anna Elizabeth Bennett – she made things like The Black Spell Brew and so forth.
LikeLike