Just compare the files of the themes that I linked to in the previous threads. You’ll find them to be very different. It’s much easier to start with a theme that has the basics to your liking. Colours are much easier to change than the layout of a theme.
If you want to learn more about CSS and XHTML, how to do it the right way instead of the looks alright way? Then follow Patrick Griffiths’ tutorials on HTML Dog.Com I haven’t seen a better and easier way to learn.