[Plugin: WordPress Post Tabs] Styling the "next" and "previous" buttons

I’ve been creating my own custom css based on the default style …

However, no matter what I do, I don’t seem to be able to get the “prev” and “next” tabs to change from the default pale grey.

This is what I have that isn’t working – I accept that this may be my coding as I’m far more of a visual type of person than a css type.

Can anyone help me get this right?

.wpts-next-tab{ float:right; background: #666; background-image: url('images/fade.png'); font-weight: bold; color: #ff0000;}

.wpts-prev-tab{ float:left; background: #666; background-image: url('images/fade.png'); font-weight: bold; color: #ff0000;}

http://wordpress.org/extend/plugins/wordpress-post-tabs/