Block Editor color picker

I’m working on a Twenty Twenty-child theme. The fronted is working very well. But Block Editor is rally a hard to style.

I’m able to set the colors picker in the editor. In function.php it works very well link:

add_filter( 'theme_mod_accent_accessible_colors', 'op_change_default_colours', 10, 1 );

    function op_change_default_colours( $default ) {
    $default = array(
        'content'       => array(
            'text'      => 'var(--unti-black)',
            'accent'    => 'var(--unti-blue)',
            'secondary' => 'var(--unti-gray)',
            'borders'   => 'var(--unti-white)',
        ),
        'header-footer' => array(
            'text'      => 'var(--unti-black)',
            'accent'    => 'var(--unti-blue)',
            'secondary' => 'var(--unti-gray)',
            'borders'   => 'var(--unti-white)',
        ),
    );

But there is one color more in the colors picker, called “background color”. How to override this color in the editor color picker?