$re = '/(?:$|^|)(red-|blue-|indigo-|cool-gray-|pink-|yellow-|teal-|gray-|orange-|green-|purple-)(50|100|200|300|400|500|600|700|800|900)(?:$|^|)/i';
$str = 'pink-300 red-400 blue-300 teal-800 ';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php