A question about Drupal Books and assigning classes to the body based on last viewed book
Thanks to No Sssweat's comment my solution for this was to use Jquery to look for the body class that controls the sidebar color then use jQuery.cookie (already packaged in Drupal just need to make sure it loads on every page) to set a cookie with that value. Then if a page visited that doesn't have the body class that indicates it was a book and therefore also doesn't have the color class then I had jQuery .addClass to add the cookie value to the body element.