public function process($string)
    {
        preg_match_all($this->tagFilter, $string, $matches);

        if (!$matches) {
            return $string;
        }

        foreach ($matches[0] as $i => $m) {
            if (array_key_exists($matches[1][$i], $this->styles)) {
                $string = $this->replaceColors(
                    $string,
                    $matches[1][$i],
                    $matches[2][$i],
                    $this->styles[$matches[1][$i]]
                );
            } elseif (strpos($matches[1][$i], '=')) {
                // Custom format
                $string = $this->replaceColors(
                    $string,
                    $matches[1][$i],
                    $matches[2][$i],
                    ColorStyle::fromString($matches[1][$i])
                );
            }
        }

        return $string;
    }