whose hair among the girls is brown ,have a sad story + costume blue ??plz add a photo if possible to prove.

You asked for a girl with brown hair, a sad story and wears a blue costume. Well, let me level with you;

Out of those you have chosen, Layla and Musa probably have the saddest stories.
Layla was forced around, and barely made any friends because her parents always cooped her up inside the castle.

Musa's mother died when she was still very young, and her father going into depression after her death - didn't really help Musa after all the trauma she had already endured. She literally had to fend for herself.

For the hair, the only one in the list you made whom has brown hair, is Layla. And for the blue costume, that would be Bloom.

(Here's the photographic proof.. I think that I could call it that. Bottom to top: Bloom (Showing her blue outfit), Layla (Showing her brown hair), Musa (Showing her past), Layla (Showing her past))

It would be Layla b/c in her believix her outfit is blue, she has a sad story, and her hair is brown.