From http://theme.fm/2011/08/using-the-color-picker-in-your-wordpress-theme-options-2152/ . See: http://stackoverflow.com/q/7954267

gistfile1.html

<input type="text" name="my-theme-options[color]" id="color" />
<input type='button' class='pickcolor button-secondary' value='Select Color'>
<div id='colorpicker' style='z-index: 100; background:#eee; border:1px solid #ccc; position:absolute; display:none;'></div>

// Color Picker for js file
$('.pickcolor').click( function(e) {
	colorPicker = jQuery(this).next('div');
	input = jQuery(this).prev('input');
	$(colorPicker).farbtastic(input);
	colorPicker.show();
	e.preventDefault();
	$(document).mousedown( function() {
		$(colorPicker).hide();
	});
});