You will have the option to change the brand color, accent color, and the company logo. A preview of the changes will also be displayed on the right side of the screen under Theme Preview
To view the changes made under banding, you can also generate and view a Railz Sites link for a business you have created.
The above screenshot displays how the Railz Sites™ will be displayed with changes made under branding.
Please see here for more information on setting up your branding.