I am looking for a children’s book that was a favorite of mine at my grandma’s house growing up. I’ve been searching for years trying to find what the name of this book was, with no luck. Despite it being fairies, and involving colours, it’s not Andrew Lang.  This is what I remember of it:

It was a hardbound book, blue or green cover, with embossed printing. So probably published prior to 1950s

The story revolved around a little girl who wasn’t very nice, so she is visited by a fairy who’s name is similar to “tintinnabulum” (I remember that very distinctly). This fairy caused a word to appear on the girl’s forehead (possibly the word KIND) that only the girl and the fairies could see; if the girl acted kindly, the word would fade with each kind act, for each unkind act it would grow darker.

The girl was then put in a hall with seven doors, one for each color of the rainbow- she needed to travel through each fairy realm, do deeds that would remove the word on her forehead, and find the door back to the hall. Each of the realms had something to do with the color of the door (Like, the light blue door’s realm was in the sky, and the dark blue was under water).

Eventually she goes through all the doors, the word is gone, and she gets to go back home.