To update the colors on your website, first navigate to Website >> Design:
On this page, you are looking for "Step 2: Choose a Palette:"
You'll see several palettes that we've created for you - click a palette and you'll see the preview on the right-hand side of this page update with those colors. The preview will show you where each color in the palette would be applied to your site - to your header/footer, menu items and headlines.
You can also try to create your own custom palette, again viewing how those changes would be applied to your site on the preview.
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.