Editing the social icons for 2020 Theme

To set social links is to create a menu with any name, saved, and then assign the location to the menu.

Add Social Icons
https://wordpress.org/support/article/twenty-twenty/#add-social-icons

To adjust the social links color, please refer theme doc on Custom Colors.

Custom Colors
https://wordpress.org/support/article/twenty-twenty/#custom-colors

We can also further adjust social links color by overriding the theme’s output using Custom CSS (use the code via Custom CSS option).

I believe this code should do it (change the color code to your linking).

.social-icons a { background: #000; }

If the above doesn’t work, try this, which has more specificity on selector to win over theme’s output

body .social-icons a { background: #000; }

If that doesn’t do it, use this

body ul.social-icons li.menu-item a { background: #000 !important; }