This has been a though in my head for a while.
So, each of the five emotions has a predominant color.
However, with some (notably Joy), there’s an accent color they also carry. Now, this might be reading a little too much into the character design, but (and some people have speculated this on Tumblr) does an emotion having an accent color of another emotion show that they have some traits of that emotion?
Most obviously, this can easily be seen in Joy, who has blue hair (and some design motifs on the dress) despite yellow being her main color. And as witnessed in the movie, Joy is not immune to crying. She can feel sadness as well, but in contrast to Sadness, she is always optimistic and sees the silver lining in everything. And as seen in the end, Sadness and Joy work together at the console when Riley cries with her parents. Obviously, joy exists even when there is sadness.
Another one I noticed, and probably viewers didn’t think about this one, but Disgust has purple as an accent color. Since purple is Fear’s dominant color, I theorized that it may be possible that disgust is represented as not only revulsion to the strange and unknown, but also having a fear/aversion to it. Riley looks at the broccoli pizza with disgust, but is she also afraid of giving it a try for a certain fear of it tasting disgusting to her?
Wow! That was extensive. Unfortunately, I couldn’t really see it with the other emotions (at least in Riley’s head) Though the mother’s Sadness wears a purple sweater, so it’s possible that she has a fear of certain thing that could make her upset.
Opinions and feedback are always welcome!