add_filter( 'generate_default_color_palettes', 'tu_custom_color_palettes' );
function tu_custom_color_palettes( $palettes ) {
	$palettes = array(
		'#000000',
		'#FFFFFF',
		'#CCDAD1',
		'#9CAEA9',
		'#788585',
		'#6F6866',
		'#38302E',
		'#AAAAAA',
	);

	return $palettes;
}