Hi,
Sorry for not replying earlier.
The white areas ar the page header and the main body of the page.
The HTML for this is a little complex so you need to see which element is being coloured white. You can do this using Firebug or the Web Developer tools in your browser.
You could try adding the following into the Raw SCSS section of the Boost theme's Advanced settings tab in Site Administration > Site Appearance > Theme > Boost:
#page-header, #region-main { background-color: transparent; }
Hope this helps?
Mary