Single Menu button color change

Hello there! I’m have a slight issue with my organization’s menu – I’m trying to get a Contribute button on the far right of the menu to be a different color than the rest of the menu (menu = blue, contribute = red). After messing with CSS for awhile, I haven’t been able to figure it out to be exactly how I wanted it, and was just wondering if this was possible!

More in detail, I’m looking to have the contribute button be red, the border underneath it to be matching (or disabling the border) and the extra space to the right of the button to be red (maybe extending the button somehow?). Any way to do that with CSS?

If that’s not possible (particularly with the extra space to the right of the button), I’d also be willing to use the special header style (the transparent one) with just the Contribute button standing out as red. Perhaps something like this: http://alisonforkentucky.com

Thanks you! Love the theme and the support I’ve gotten with it so far.