You can choose from a number of palettes (color themes) when building your website. Color themes help generate an aesthetically balanced appearance across the various pages you create.
Additionally, you can choose an accent color; a favored color helpful in customizing certain aspects of your website's appearance and particularly useful for matching or complementing your logo colors.
Color themes and accents are distributed differently from template to template, so you are encouraged to experiment between them to find the balance you like best.
Websites > Single Property (or Multiple Property) > Design & Template and click on the "Change Design" button at the bottom of the page. Then click on the "Colors" bar in the right hand bar menu to bring up your color theme options.