basic CSS advice (changing colors)

Hi all!

Hoping someone more savvy could help me figure out the right CSS to add in the Customizer to do two things on the above site:

1) When you scroll down the page on mobile/small screen, the bars in hamburger icon in top right go from white to black. Would like them to stay white but can’t get the right selector path to make that change!

2) Same basic question for the three large icons just below the fold (currently light blue, orange, and purple). Is there CSS I can add to change those colors? I am using the free version of the Highlight theme and under the free settings I can’t adjust those colors. Not sure if that means I’d need to upgrade the theme to change those colors, or if I am just not seeing how to select w/CSS to change that way. (Not trying to be sneaky! if it’s a theme restriction fine by me, not a big deal; just wanted to make sure.)

The page I need help with: [log in to see the link]