Navigate to the Control Panel > Website Tab > Setup > Look & Feel.
In the Site Editor Toolbar, click Colors.
Color schemes are predefined collections of complimentary colors used for various elements of the website, including backgrounds, header backgrounds, header font colors, text colors, etc.
Select a category from the options on the left and then click a color scheme image to select it. Click Save to preview your website with that color scheme or Cancel to close the dialog without saving. You can override these color selections using the Row or Cell Style options in the Template Builder.