I don't really get what you mean, but if you want to change the color of the background, all you got to do is to set the background color as white(note that theres also a foreground color), then "CTRL + Backspace" on the background layer itself. ^_^ Reliqua
either... 1. make sure your foreground colour is white then just make a box thats the sime size as your work 2. when u click new in the menu that comes up about the sizes and other things ther is a backgpround box go in the drop down - menu and click on white hope this helps you m8