"If an audience can intuit characteristics based on color, characters can be smart enough to want others to intuit them too, particularly in the case of someone like Sally who is trying so hard to project a false exterior."
That's valid, and that, I'm sure, is the reason she was a given a red dress.
However, there are color choices that just don't work on characters because they disrupt the bigger picture of the work. Giving Sally the boldest color on stage is not a good decision, particularly a color that signifies so much. There are other ways Sally could achieve a false exterior without red.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."