To update the colors on your website, first navigate to Website >> Design:
On this page, you are looking for "Choose a Palette":
You'll see several palettes that we've created for you - click on any palette to select that color palette for your site. The palette would apply to your header/footer, menu items and headlines.
You can also try to create your own custom palette, by clicking "edit" under the palette:
Note: once you "Publish" the changes here, they will be applied to your site immediately, without compliance review/approval.
Note: users with an Exclusive theme cannot change their colors from this screen, due to custom coding.