By means of the function "set" it is possible to set a separate background for the pages, either an image (this must be accessible via web access) or as a hexadecimal color value.
An image must be reachable via FTP, HTTP or HTTPS, for example:
ftp://example.com/pictures/background05.jpg
Or:
http://www.example.com/pictures/background08.gif
Or:
https://www.example.com/pictures/background11.png
If, on the other hand, you want to set a color as the background, you must specify this in the hexadecimal format 'RRGGBB', where 'RR' stands for the red component, 'GG' for the green component and 'BB' for the blue component.
For example:
FF0000 = red 00FF00 = green 0000FF = blue
The background can also be set using an URL/Get - parameter 'background = [URL or color value]', for example: