Color theme changes don't save

Hi, I have been playing with using different colour themes on my site to see what I liked best. It (selecting a theme) was working but now when try and change the selection in the 'Edit Theme' section it doesn't save. The box on the right of the edited section I'm working on just stays the same.  I am now stuck with some colour themes I don't want on a couple of pages.

Please Help!

Many thanks

Thank you so much, that has worked!!