This is absolutely gorgeous! I love your style too, there's so much character in it.
As for why Chibiusa's hair is pink; Quote: "In anime and manga, eye color and hair color have nothing to do with relationships. I have read up on the style and the "color" is only for the viewer of the anime or manga to identify specific characters or more important main characters. Traits are given to them as an identity not because of their birth from one family or another. If it was that way, Usagi would be out of place with her mother having blue hair, father having black, and brother having brown." I read Naoko Takeuchi wanted Chibiusa to resemble an albino rabbit. Her hairstyle was intended to look like rabbit ears and that's why her eyes are red.