Here is one of the easiest ways to change ALL the colors on your website using just one file!

1 Make sure you followed my CSS tutorial. Copy and paste all of that into a new document.
2 Save that document as style.css.
3 On the top of all of your layout pages, insert this code between the HEAD tags:

<LINK REL=stylesheet HREF="style.css" TYPE="text/css">

Now, whenever you need to change colors on your layout, just edit your style.css, upload it to the directories needed and you're good to go!