funzione codice esadecimale colori?

function hex2rgb($hex) {
   $hex = str_replace("#", "", $hex);

   if(strlen($hex) == 3) {
      $r = hexdec(substr($hex,0,1).substr($hex,0,1));
      $g = hexdec(substr($hex,1,1).substr($hex,1,1));
      $b = hexdec(substr($hex,2,1).substr($hex,2,1));
   } else {
      $r = hexdec(substr($hex,0,2));
      $g = hexdec(substr($hex,2,2));
      $b = hexdec(substr($hex,4,2));
   }
   $rgb = array($r, $g, $b);
   return $rgb; // ritorna un array con i valori rgb
}

$rgb = hex2rgb("#colore-esadecimale");

$rgb = hex2rgb("#FFFFFF"); 
$red = $rgb[0]/255;
$green = $rgb[1]/255;
$blue = $rgb[2]/255;
if($green>0.75 AND $red>0.75 AND $blue>0.75){
	echo 'Bianco';
}
else if($green>0.5 AND $red>0.5 AND $blue>0.5){
	echo 'Argento';
}
else if($green>0 AND $red>0 AND $blue>0){
	echo 'Grigio';
}
else if($green==0 AND $red==0 AND $blue==0){
	echo 'Nero';
}
else if($red>50 AND $green<10 AND $blue<10){
	echo 'Rosso';
}

<?php
$esadecimale = "esadecimale-senza-#";
$colore = file_get_contents("http://stubborn.altervista.org/tools/hex-to-color.php?hex=".$esadecimale);
?>