What is best--a full day or half day of wine touring in Colmar?

How much time do you have in the area? There are usually trade-offs. I loved the Unterlinden Museum in Colmar and the gorgeous (if touristy) streets of the old town. I have no interest in wine or vineyards, but the little towns are very pretty.

I assume you mean wine touring "from" Colmar rather than "in" Colmar, since while there are lots of wineries in the Colmar area, I don't know if there are any actually within the city. I visit lots of wineries wherever we go in France, but I would consider a full day tour just visiting wineries to be too much. On the other hand, if the day included visiting the villages that the wineries are in, that would be different. There are hundreds of wineries scattered throughout the charming villages of Alsace.

Have you done wine tours in the past?

My wife and I prefer quality over quantity. Even though the Napa/Sonoma region has hundreds of wineries, we never did more than two tours in a day. I guess we could have done a couple of more if we spit, but I'm too Scottish for that. ;-)

For me, the best experience is to combine a tour of a winery with a food and wine pairing for lunch. Most wines should be served with food and the best way to really judge a wine is to pair it with an appropriate food dish.

Unless you spit, you're normally too tipsy after two wine tastings to be able to tell anything about the wine.