Unable to modify colours, fonts, etc.

I have installed the gk_news template on two Joomla 3 installations, one with my real site content and another using the test installation with all your date. The latter works fine and I can change colours, fonts, etc. when I go into the template options. On the "real" installation, however, I am unable to do so. i.e. When I make changes to the colour scheme or fonts under options, these have no effect on the site. Why might that be so?

Are you sure that caching is disabled?
If so - please provide an url to your site and some info on changes you have made.

The URL is http://joomla1.africafiles.org/

When I go into the template manager and attempt to edit a style (like changing a font or the colour scheme), nothing happens. I have disabled all caching and this still occurs. The site includes a number of modules including multi-categories and mighty sites - could one of those be interfering?

I installed the test files on the same server and I can change colours, fonts, etc. without problems there.

Perhaps one of 3rd party modules messes with the code. If on clean installation everything is fine, you should check whats causing the problem by selectively disabling each of 3rd party plugins and checking if custom configuration works fine.