As a Baby the Princess did not like elderly women including her own grandmother Princess Charles of Hesse - I don't think that she had it lateron though =)
I've also read that. When her paternal grandmother wanted to hold her, Ella (a baby at the time) showed a somewhat rebellious reaction, but apparently she appeared very calm and happy when her other grandmother Queen Victoria held her.
Her hair may have been auburn, or lighter, like a brownish-reddish colour. I've read that her hair was a little bit darker than Alix's.
I also don't know about the exact height, but from photographs I've seen, Ella looks a little bit taller than Alix, in my opinion, though I could be wrong.
Ella liked to take care of herself - She had a lotion of cucumber juice and sour cream for her face and she always protected herself from the sun. I think she had designed a lot of her own clothes, including the one she wore as a nun. Clearly she enjoyed fashion and she also liked to paint, and design a lot, such as when Nikolai and Alix were first married Ella decided to arrange their rooms at Tsarskoe Selo.
You can read the biographies of Ella at the main AP page to find out more. =]