Vatican & Colosseum tickets
 

My husband & I will be in Rome early March. Planning to order tickets for Vatican Musuems and Colosseum online. Can anyone tell me if I can buy them once we get there and show tickets on my phone or do I need to buy before we leave and print them out first? We are staying at an Airbnb and won’t have a printer. Thanks

The Colosseum ticket would say:
If you have requested option "print@home" you will need to print the pdf attached to this email and go to the dedicated gate without going through the ticket office;
However, what they are looking for is the booking code. If you were thinking of doing the Underground Tour in English, you are out of luck. Most March tours are already sold out or just one slot available.

If you go to the Vatican Museum site, it would tell you
The applicant is asked to print off the voucher (it is also possible to show it on a smartphone or tablet)
The March dates are showing availability. 9am and 10am slots seem to be popular.

Thank you! I appreciate the help

We bought both tickets and printed both while still at home.
I prefer to err on the safe side and have a print out with me whenever possible.
I know that it's as possible to lose paper as to run low on smartphone battery, though.

You probably know already that the ticket to Colloseum includes admission to the nearby forum and is good for 2 days.
We opted for the ticket with dedicated/reserved entrance times for the Colosseum.