To set the background colour of a page:
1. Left-click on the page you wish to apply a background to.
2. Left-click on the icon furthest to the right (the icon that looks like a can of paint) from the toolbar at the top right of the editor.
3. Below the words 'Page Background', click on the square next to the page you wish to change ('Left' or 'Right'), then select a colour from the drop-down list. Select 'other' for a full colour pallette.