Can I change the WordPress default color?

You’re in the wrong area… …those are background colours for the theme, what you’re looking for is the Additional CSS at the bottom of the customizer. (Screenshots below.)

In the Additional CSS you’ll have a text area where you can put your own CSS, use this:

body:not(.overlay-header) .primary-menu > li > a, body:not(.overlay-header) .primary-menu > li > .icon, .modal-menu a, .footer-menu a, .footer-widgets a, #site-footer .wp-block-button.is-style-outline, .wp-block-pullquote:before, .singular:not(.overlay-header) .entry-header a, .archive-header a, .header-footer-group .color-accent, .header-footer-group .color-accent-hover:hover{
    color:#000;
}

That’ll set all of the menu items that are currently pink to be black.

Additional CSS in Customizer

The CSS rules