Primary Menu bar Colour

Hi! I'm wondering how do you change the default black colour for the primary menu bar that runs across just below the website name to green? Also, I believe on Catch Box, the green colour bar appears on both the desktop and mobile sites. On Catch Flames, the desktop site has the black bar, but the mobile site has no colour bar. How can we add that same same Catch Box has? Thanks, you guys are awesome!