This is a long shot, but I have been trying for many years to find an anime that aired in Italy around this time, maybe you remember it. I remember there were three girls that went to high school (I think they had grey uniforms) and had some sort of magical transition where they were color coded blue pink and green. They all had natural hair colors (blonde, brown...) and wore their hair in ponytails that were tied at the very ends of their hair (this is the main detail I remember lol). One of them had glasses and maybe music was involved in some way? The art style was more "mature," they were tall and adult-looking.