From the FAQs on the Scottish Tartans Museum ("home" of very own Matt Newsome!):

Hunting and Dress tartans also cause much confusion among the uninitiated. These names also refer to color changes, not to any kind of actual usage. Dress tartans are based on the old arasaide tartans worn by women in the Highlands of the 17th and 18th centuries. These tartans had a white base. Today's dress tartans are made by replacing one of the prominent field colors of a tartan with white. These are used most frequently in dancing, but are often seen in formal and even casual occasions. There is no rule that says one has to wear a dress tartan to a formal occasion. Most men do not. Hunting tartans came about in the mid 1800s when two versions of the MacLeod tartan were published in a book called Vestiarium Scoticum (later proved to be a fake--but there is not enough room to go into the history of this important book here). There was a bright yellow MacLeod (MacLeod of Lewis), called "dress" and a green and blue tartan (MacLeod of Harris) called "hunting." The green tartans became very popular after this and most families who had bright red or yellow based tartans designed alternate tartans with a green background (or sometimes brown) and called them "hunting." Families whose tartans are mostly green do not usually have alternate hunting tartans. These tartans actually had little to do with hunts.

Whether you wear a modern or ancient tartan, hunting or dress, or any other form of your tartan is up to you.

-- http://www.scottishtartans.org/faq.html
Cheers,

Todd