Tutorial for creating an admin options page to edit css

Hello – looking for a tutorial on how I would create an option to edit certain css colours etc.

Say I wanted an option called “page options” in the dashboard, and when I click on it I wanted to be able to set the background colour of my theme that way (by typing the colour code into a box there). Rather than having to go into the style.css file.

If anyone has a link to a tutorial that’d be great (or in the codex). I can’t find one, I think it’ll be sooo much better for my clients if I learn this (to stop them breaking things 😛 )