Now make sure the width and height its 400px so that you can get a square shaped favicon with the background color as white.
Now select the desired background color you want to use for your favicon by clicking set foreground color as show in the figure. Choose a nice web 2.0 color from the Color library.
After selecting, drag your mouse from the outermost top of the project to its extreme end via +y to –y axis and leave down to get a color background.
Creating a simple web 2.0 favicon – SankarAnand.com