public function simpleRgbDistance($color1, $color2)
    {
        $deltaR = ($color2->r - $color1->r) / 255;
        $deltaG = ($color2->g - $color1->g) / 255;
        $deltaB = ($color2->b - $color1->b) / 255;
        $deltaE = $deltaR * $deltaR + $deltaG * $deltaG + $deltaB * $deltaB;

        return ($deltaE < 0)
            ? $deltaE
            : sqrt($deltaE) * 57.73502691896258;  //  / sqrt(3) * 100;
    }