Fix up and expand colour schemes

So far the colour schemes are simply copied from skeletontheme. Need to adapt and add new schemes. Includes:

• Remove any unused colour selectors. For example, currently the theme has only one top of page border, not two.
• Add any additional selectors. Do we want to be able to select shading colours for elements like the menu bar?
• Revise existing and add new schemes. Worth looking at other adaptivetheme subthemes for colour scheme ideas.