How can I change the menu color in the Dawn theme?

Store Design
8

@ebon
Paste this code for font-size.

summary.header__menu-item.list-menu__item.link.focus-inset {
    font-size: 20px !important;
}
a.header__menu-item.header__menu-item.list-menu__item.link.link--text.focus-inset {
    font-size: 20px !important;
}

Thank You.