One of the things that separates anime from other animation is simply the way it looks. The eyes are often what people notice first. My statement was partly correct - it is a style of drawing, and it is definitely present in anime. But there is another side to it as well. This reflects upon her, as she is not only the youngest member of the group, but she cares deeply about what happens to the others.
Hair color is another thing people notice.
I remember watching Neon Genesis Evangelion once at my home, and my mother walks into the room and sees the character Rei Ayanami - a young girl with short blue hair. I really didn't know at the time. Manga is traditionally drawn in black and white, and so different shades were given to different characters to help differentiate them from each other. In anime they were given different colors for the same reason, however it is not the only reason. Blue hair can represent a calm personality, fire-red hair can represent a hot temperament.