Rainbow Tales, #1, Cover

Published in London in 1960 by Dean & Son, I received this book as a present from an aunt, and loved it dearly.
Interestingly, it says "character created by Honoria Plesch," but has a different author and illustrators. I didn't even know they were 'creating" characters back then.
The stories are by Diana Marr-Johnson. The illustrators are Janet & Anne Grahame-Johnstone.
The stories feature Rainbow, a magical being, who often, not always, appears in water drops to come to the aid of people in trouble.
I never knew anyone else who had this book, but perhaps I'll discover them now!