passing variable via url ( newbye question)

I can pass one variable using the url on this way http://myadress/php/mypage.php?modo=123 and to read i have the code echo $_GET['modo']."<BR"; That's work fine on 4.21 How can I pass and read 3 variables instead of one ? I nedd to pass mode = 123 color= red size=3 using the url I tried http://myadress/php/mypage.php?modo=123&color=red&size=3 and to get echo $_GET['modo']."<BR"; echo $_GET['color']."<BR"; echo $_GET['size']."<BR"; but does not work How can i do that