As I and others so often do, I'm going to recommend a visit to the Vivienne Files, especially the postings on packing: http://www.theviviennefiles.com/p/packing.html and more especially the ones on 4x4 wardrobes: http://www.theviviennefiles.com/p/four-by-four-wardrobes.html.
Look at the well-illustrated concepts and ideas and don't be freaked out by the prices of some of the things you can click through to, or by the number of items she takes. She thinks she packs light, but it definitely ain't RS style. Also don't be too annoyed by the seeming emphasis on things more appropriate to cool weather than to the warm and humid weather you will experience in Italy. For me the gift is the color combinations and the kinds of accessories that add punch.
In response to what others have said, I agree about a lightweight scarf or 2. You will be surprised at how many women you will see wearing them and they can relieve the boredom of all neutrals all the time. They can also absorb a bit of sweat and be easily washed at night. And they can act as a bib to catch that red sauce instead of your top. You can also take a print top that is red sauce ready.
I have taken skirts before and find that I just do not wear them as much as pants on a trip, so I took/wore my last skirt on our trip this past fall. I find they take up more room in my little spinner than they are worth and I just look and feel better in pants.
I have made 2 trips with all blue all the time, just different shades of it. Almost any blue makes me look better and I love blue shoes and always have.
Black hasn't ever been much of a friend to me on our trips. My husband absolutely refuses to wear black because it gets so much lint on it in so many situations. A lot of how dirty anything gets may depend on the fabric itself more than the color.
Please heed the advice of others about the comfort of your shoes. You will walk and stand more than you can possibly anticipate. Try to imagine 6-8 hours per day. Keens and Clarks do not work for me at all, but if they work for you, wear 'em. My latest faves for comfort and support are Abeos from the Walking Company (https://www.thewalkingcompany.com/abeo-casualshoes-womens). I had an employee once who swore than red is a neutral color. If you stick with the Keens, be bold, get the red and coordinate your other clothing around your silver and red shoes.
Being baffled when you don't normally dress this way is a challenge. What I've learned here about packing light in combination with what I've learned from the Vivienne Files about coordination has actually changed the way I dress. It's hard to believe, but my closet now has fewer items and is more versatile.
And I have a blast each trip deciding what I'll wear on it, "shopping" in my closet for things that will work and for real to add to them. Including what I wear in transit for our month-long trips, I usually take 3 pairs of pants, 8 tops (including tanks) and one outerwear piece (like a cardigan or a rain jacket). I take 2-3 pairs of shoes that I wear outside the room, depending on the destination. If time permits, I do like to change my shoes after a long day of being on my feet.