I got curious about this so I looked it up.
By NFL rule, the home team gets to choose which jersey it will wear – light or dark. The visiting team must then wear the other. By tradition, most home teams choose dark, but Dallas chooses to wear light at home - and here’s the answer to the question - for superstitious reasons. Consequently, Dallas would wear light all the time – except – if they visit a team doing what they do. I don’t understand why their opponents don’t always do the same thing when Dallas is the visitor, forcing them to wear dark.
If you’ll recall, the Patriots wore white at home to throw off the Cowboys a couple years ago.
Read more: http://tinyurl.com/873gj94