public function __construct(Tracker $tracker)
 {
     $this->tracker = $tracker;
     foreach ($this->existing_colors as $color) {
         $this->colors[] = array('color' => $color, 'selected' => $color === $this->tracker->getColor());
     }
 }
 public function tracker_color()
 {
     return $this->tracker->getColor();
 }