If you want to make an image which has several colors, use the free Irfanview http://www.irfanview.com/ and then use it as a background image repeated vertically.
If you don't want to use a background image, you can code three divs with float: left so that they are side by side and put a different background color in each.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.