Italy/Switzerland/France Train Advice

We purchased Eurail passes last year for our family of four. We used it in Italy, the Netherlands and England. I will say financially it was a wash for us. My husband had a senior citizen ticket, our son and daughter were in their early 20s and thus eligible for student tickets, and when I bought the tickets they were “on sale” at an additional discount; also, I bought first class tickets. However, unless something has changed from May/June 2022, I would NOT include tickets for Italian trains in your Eurail pass—it was too cumbersome/ impossible to book seats ahead of time. I was only able to do so once and for us, it was just too inconvenient. Booking the Eurostar was easy with the Eurail pass and I think the savings there alone was most likely worthwhile for us, but that was the only advantage I found, given all the caveats for a Eurail pass. My husband and I are returning to Italy this year and really enjoy traveling by train. For this trip, we will be booking directly with Trentalia or Italo (mostly Trentalia).
I suggest checking out the Man in Seat 61, his information is thorough and well organized https://www.seat61.com/

Do not get an Eurail pass. It is cumbersome in Italy, a big pain in the posterior in France and not good value in Switzerland.

Just buy train tickets. Book them in advance, and book them, if possible, end to end.

Venice - Murren for example you can book on www.sbb.ch, and the same applies to Murren - Colmar. You are probably not spending enough time in Switzerland to warrant getting a pass.

Trenitalia has a "Me & You" pass. Very inexpensive rail, especially if you book well in advance. Eurail is not a very good option, in my opinion. Purchasing in advance direct is always a better deal.

Book Trenitalia for your journey from Venice to Murren, as it should be less expensive than Swiss Rail. Same for the journey to Colmar, book SNCF, if possible. I have used them the opposite direction - Colmar to Lauterbrunnen. Cost savings could be significant. Also, when in Murren, you will probably want to purchase a Jungfrau Travel Pass. While it is pricy, it is cheaper in the long run, especially if you will be in the Valley for multiple days. Navigating Swiss rail travel discounts can be a mind-bender. There are half-fare cards, travel passes, etc. I take the easy way out and just purchase the local travel pass and book all other rail via destination rail services. YMMV.

You cannot book Venice to Mürren on Trenitalia, nor can you book Mürren - Colmar on SNCF. That is why I suggested booking this with SBB, where you can.