To change your Subscription cover colors:
Log into your account at chatbooks.com and click into your bookshelf
Click on the subscription you'd like to edit
Click on the settings wheel in the top right corner
Click "Manage Subscription"
Click "Cover Color"
Select the cover option you'd like and click "save"
Click "Done"
Click the back arrow in the top left corner to get back to your subscription
You can also edit your cover options for your Monthbooks/Minis on the Chatbooks app. Learn how to do this here.