Can someone please help with a simple CSS coding change?

I bought this wordpress theme a while ago: http://choco.dream-theme.com/ and have been trying to change the color of the menu bar from black to something else.

I've contacted the people who've written this theme and they said it's possible to change the color and it's pretty simple but if I didn't have intermediate knowledge of CSS, I should just hire a freelancer... I would have hired a freelancer but I just spent $40 buying this wordpress theme. I was hoping they'd at least give me some support.

Can anyone help me in how I go about changing the color on this?

Thanks