Are they worth it? If so, would it be best to buy in advance or are there people outside any given day to negotiate private tours with? Projected tour is mid-March on a Friday.
Definitely get the underground tour! We were there last May and it’s so interesting! Buy in advance for sure!
I just want to warn you that Underground tour tickets are difficult to get. You can still have a great experience at the Colosseum with a regular tour, but I would go for a tour since everything makes so much more sense if you know what you are looking at.
Buy in advance . Here is the link for the official ticket site.
https://www.coopculture.it/en/products/ticket-colosseum-roman-forum-palatine_24h/
....are there people outside any given day to negotiate private tours
with?
I would think there's a pretty big chance that any ticket or tour being 'negotiated' on the street for the Colosseum is doing so illegally. Please buy from a verified source and don't risk supporting a 'dark' operation. This is from the pre-COVID era but probably still applies.
https://www.wantedinrome.com/news/rome-cracks-down-on-illegal-trading-at-colosseum.html