1. Click the page itself (the frame of the page should be highlighted in orange).
2. Click the Background button located on the upper style toolbar.
3. Click the Color button on the background panel
4. Choose the background color for the page
5 . By default changes made to the page will apply to the master template and all pages based on it.
Need more help? Try:
1. How to change the background image of the master template?
2. How to change the background color of a website?
3. How to change aspects of an individual page without affecting the master template?