Over the years I've come across a few observations that I have found rather interesting, and so this image here is my way of illustrating that observation so that others can appreciate it.
What I've done here is presented a series of pairs and trios throughout animated film and television, all female (save for special exceptions at the bottom) who all have very similar patterns of hair color. Some have yellow, orange, or red hair, while their partners have purple, black, or variants of blue hair, some of which can all artistically be the same thing. In the trios, however, there is the addition of the blond-haired character.
The personalities of these characters is never consistent, but the character design choices that led vastly different creative teams to come to the same relative conclusions is quite interesting to study, especially when designing your own characters.