Mr. Men meets The Color Monster--with a unicorn!--in the third book in this series that taps into the current trend of books about childhood emotions, this one about sadness.A little unicorn's rainbow-colored mane shifts to a single color when he's feeling a particularly strong emotion. It seems like a storm comes over him when he's sad, and his mane turns deep blue. But when he repeats a breathing exercise, the clouds clear and his rainbow returns--and if he ever feels sad a