Function to determine if a Hex color is "light" or "dark"

functions.php

<?php
function isColorLightOrDark( $color ) {
	$red = hexdec(substr($color, 1, 2));
	$green = hexdec(substr($color, 3, 2));
	$blue = hexdec(substr($color, 5, 2));
	$result = (($red * 299) + ($green * 587) + ($blue * 114)) / 1000;
	if ( intval($result) > 128 ) {
		$lightdark = "light";
	} else {
		$lightdark = "dark";
	}
	return $lightdark;
}