For Wordress sites, this depends on the theme that you are using. Please contact your Project Manager or open a ticket to contact Support if you need assistance. If you have gone through the Smart Therapy Websites Program, please see the Wordpress Tutorials that your Project Manager sent when you went live to get started with content editing.
For Squarespace sites, you can change most colors from the dashboard. Login to your account, click Design on the left hand side of the screen, then click Style Editor. Here you will find a color picker for the main elements of your site. If you need help, please contact your Project Manager or open a ticket to contact Support.