class ColorGuessBasedOnIblock extends ColorGuess
{
   public function initColorReference()
   {
      $this->colorReference = array();

      $rsData = CIBlockElement::getList(array(), array(
         "IBLOCK_ID" => $this->colorReferenceId,
      ), false, false, array("ID", "NAME", "PROPERTY_RGB"));
      while($arData = $rsData->fetch())
      {
         if ($arData["PROPERTY_RGB_VALUE"])
         {
            list($r, $g, $b) = explode(",", $arData["PROPERTY_RGB_VALUE"], 3);
            $this->colorReference[$arData["ID"]] = array(
               "R" => $r,
               "G" => $g,
               "B" => $b,
            );
         }
      }

      return true;
   }
}

$colorG = new ColorGuessBasedOnIblock(6); // Справочник
$colorG->handleIblock(1, 97);
 

   public function guessColor()
   {
      $histogram = array();
      foreach ($this->colorReference as $key => $arData)
      {
         $c1 = $this->rgb2xyz($arData);
         $c1 = $this->xyz2lab($c1);
         $c1["C"] = 0; //счётчик близких цветов.
         $histogram[$key] = $c1;
      }

      $cache = array();
      $width = imagesx($this->image);
      $height = imagesy($this->image);
      for ($x = 0; $x < $width; $x++)
      {
         for ($y = 0; $y < $height; $y++)
         {
            $a = imagecolorat($this->maskImage, $x, $y);
            if ($a == $this->maskColor)
               continue;

            $rgb = imagecolorat($this->image, $x, $y);
            
            $rgb = $rgb & 0xFFFFFF;
            if (!isset($cache[$rgb]))
            {
               $imageColor = array(
                  "R" => (($rgb >> 16) & 0xFF),
                  "G" => (($rgb >> 8) & 0xFF),
                  "B" => ($rgb & 0xFF),
               );
               $imageColor = $this->rgb2xyz($imageColor);
               $imageColor = $this->xyz2lab($imageColor);
               $distances = array();
               foreach ($histogram as $key => $referenceColor)
               {
                  $dL = $imageColor["L"] - $referenceColor["L"];
                  $dA = $imageColor["a"] - $referenceColor["a"];
                  $dB = $imageColor["b"] - $referenceColor["b"];

                  $distances[$key] = $dL*$dL + $dA*$dA + $dB*$dB;
               }
               asort($distances);
               reset($distances);
               $cache[$rgb] = key($distances);
            }
            
            $key = $cache[$rgb];
            $histogram[$key]["C"]++;
         }
      }

      \Bitrix\Main\Type\Collection::sortByColumn($histogram, array("C" => SORT_DESC), '', null, true);

      reset($histogram);
      return key($histogram);
   }