Hi Terri,
There are several player properties that control text color. For example, Base>Link Text changes the font color for the course title and topbar player tabs. And List Item>Normal Text, List Item>Selected Item Text, and List Item>Viewed Item all control the color of slide titles in your course sidebar.
You can see which player color properties affect each element of the standard desktop player in the PDF job aid above. And this user guide explains how to edit player colors in Storyline:
https://community.articulate.com/series/74/articles/articulate-storyline-360-user-guide-how-to-change-player-colors-font-sizeJust let us know if you need help identifying the color property for a particular player element. :)