Source

File: wp-admin/includes/class-custom-image-header.php

public function js_1() {
		$default_color = '';
		if ( current_theme_supports( 'custom-header', 'default-text-color' ) ) {
			$default_color = get_theme_support( 'custom-header', 'default-text-color' );
			if ( $default_color && false === strpos( $default_color, '#' ) ) {
				$default_color = '#' . $default_color;
			}
		}
		?>
<script type="text/javascript">
(function($){
	var default_color = '<?php echo $default_color; ?>',
		header_text_fields;

	function pickColor(color) {
		$('#name').css('color', color);
		$('#desc').css('color', color);
		$('#text-color').val(color);
	}

	function toggle_text() {
		var checked = $('#display-header-text').prop('checked'),
			text_color;
		header_text_fields.toggle( checked );
		if ( ! checked )
			return;
		text_color = $('#text-color');
		if ( '' === text_color.val().replace('#', '') ) {
			text_color.val( default_color );
			pickColor( default_color );
		} else {
			pickColor( text_color.val() );
		}
	}

	$(document).ready(function() {
		var text_color = $('#text-color');
		header_text_fields = $('.displaying-header-text');
		text_color.wpColorPicker({
			change: function( event, ui ) {
				pickColor( text_color.wpColorPicker('color') );
			},
			clear: function() {
				pickColor( '' );
			}
		});
		$('#display-header-text').click( toggle_text );
		<?php if ( ! display_header_text() ) : ?>
		toggle_text();
		<?php endif; ?>
	});
})(jQuery);
</script>
		<?php
	}