This must JUST have been posted in the "News" section of the website:
https://www.coopculture.it/en/the-colosseum.cfm
CLOSURE OF ARENA, UNDERGROUND AND THIRD LEVEL
Due to the complex setting-up and taking down of the Via Crucis (my note: Way Of The Cross procession) during the Holy Easter, from April 1st until April 12th the access to the arena, the underground and the third level of the Coliseum will be closed to the public.”
Obviously, any tours which include these areas will not be available for bookings, and I'm sure those already booked will be offered a refund or an alternative tour...although what's left to visit will be the standard areas included in the "ordinary entrance" ticket. That's aside from the Forum/Palatine, of course.
I'll scour the site further to see if I notice any other changes but wanted to get this out ASAP as I know it affects some of you.