desktop themes and/or display properties

I've tried changing the color of my browser first by going
to desktop themes and choosing a theme. When I did this
and pressed apply like I have done before, the writing and
icons on my taskbar and browser changed but the color
remained the same. I then tried going to display
properties and choosing a scheme to use but the same thing
happened here that happened with the desktop themes. It
comes up saying "not responding" in both situations. What
could the problem be and what should be done about it?
Thank you.