The Havana theme includes the option to change the colors of some of the elements within the theme.
To set a color, navigate to Appearance > Customize > Accent Color and use the color picker to select your color.
Note: The Havana theme includes a color contrast detector to help make text easier to read depending upon the colors you select. For example, if you choose a light Accent color, the button text will automatically be changed to dark gray. If you choose a dark Accent color, the text will automatically be changed to white.
Be sure to click the Save & Publish button at the top of the customizer to preserve your changes.