Change colour of page navigation menu

Hi, 

I need to change the colour of the page navigation menu on my site: http://jet-force.co.uk/

It's visible in the narrow mobile view and is dark green (the same menu where the search magnifying glass is located). 

Please can you tell me where this colour can be changed? 

Thanks, 

Nick. 

You have options to change the colors of header in your Plumbing WordPress theme please go to wp-admin >> appearance >> cutomize and header options and you can start playing with colors if something is not working as it should then kindly post your WordPress logins and desired colors so we can test thanks