Hime-chan no Ribon Colourful

Tomboyish Himeko loves sports and playing with the boys, but longs to be a feminine, gentle girl like her name implies. When it looks like all is lost, suddenly a familiar face gives her a magical hair ribbon that grants Himeko the ability to appear like anyone in the human world in return for being a magical observation subject.

This is a remake of the classic shoujo manga and anime of the early 90's by Mizusawa Megumi.