I don't know!
When I went on a cruise to Mexico a couple of years ago, (in February) I wasn't dressing 'winter-y'. That said, I did have some lighter weight black and navy dress pants, which came in handy for the fine dining nights that weren't the formal nights. I wore more spring-like tops with these. During the day, it's pretty casual.
Also - a trench coat really came in handy for getting to and from (from airport to airport and such).
Shoes seem to take up a lot of space in one's luggage, and for the cruise, I was able to get away with just *one* pair of very comfortable slides/sandals, and one pair of fancy shoes for those formal nights. The slides/sandals were sort of the kind of thing that could look dressy, but could also look casual during the day as well. The all-purpose pair I took looked something similar to these (in black):
http://clarks.zappos.com/n/p/d...../2750.html
http://www.eccousa.com/shoes/w.....etail.aspx
Perfectly fine with those dress pants, but also looked nice with white jeans and such.
And the best part was making certain that these 'all purpose' shoes were going to be comfortable, which was great when stopping in different ports.
You have asked a very good question. In Mexico, it didn't seem like people were dressing in wintery-colours, and this was February.
That said, I've been to Florida in the winter, and people *do* wear sweaters and fall/winter type clothes.
Hopefully someone else might know about whether or not people will be wearing winter colours.