public function getSelectedGroup()
    {
        $source = $this->getSource();

        if ($source) {
            foreach ($source as $groupName => $values) {
                if (is_array($values)) {
                    if (array_key_exists($this->value, $values)) {
                        return $groupName;
                    }
                } else {
                    throw new InvalidArgumentException('To use GroupedColorPaletteField you need to pass in an array of array\'s');
                }
            }
        }
    }