Colors play an important role in everyday life. They are also important in our writings as we must “show” how someone is behaving, not just “telling” our readers about it.
Telling: Sally was happy that Billy-John asked her to go fishing.
Showing: Sally rummaged through her closet until she found her yellow sundress. Bright and sunny, just like the day Billy-John asked her to go fishing.
This linked article is a good primer on what the different colors mean from a psychological standpoint.