Sub Menu Colours

Hi,

Trying to change the submenu colours on this site:

http://m62.siteground.biz/~contenta/beingwellyoga.com/

I saw this post: http://blueowlcreative.com/support_wp/forums/topic/change-color-to-sub-menu/ but I don’t see any options to change the submenu colours in the theme options or in the front-end customizer.

Is this something done via CSS? If so could you provide the code for:
Background: white
Submenu items: #283891
Submenu hover: #13a89e

Thanks again,
Casper