All themes include the option to change the colors of some of the elements within the theme.
Go to Appearance > Customize > Colors to change the colors, if desired.
Click Select Color to reveal the color picker and choose a new color for each available setting.
Please note that all themes have different color settings. The image below is an example only:
Some themes include transparency controls which allow you to control the opacity of the custom color. This is located below the color picker. See screenshot below:
Be sure to click the Save & Publish button at the top of the Customizer to preserve your changes.