You can purchase tickets online for the coliseum (and other museums) through Pierreci which is somewhat of an official Rome booking site authorized by the Cultural Ministry. When you click purchase, it will probably take you to ticketclic.it
http://www.pierreci.it/do/show/list/0

well, since 2006--I've traveled a bit more. soon, I will be at 51 countries traveled. so many more to go.......
surfingmomma

sorry, fellow travelers, don't know how i posted this message of # of countries traveled to this question--
i need more coffee this morning.....
surfingmomma

According to the Vatican website the
entreance times are from 10.00 to 13.30 on Sat 26th of May.......

So who do you believe??

Entrance times are not tour times. Here is the Vatican link for their tours and as you can see, the last tour time on Saturday's is 11:30.
http://mv.vatican.va/3_EN/pages/z-In...zi_Visite.html

There are audio guides you can rent if you would like to tour on your own.