You don't have to wear white however wearing a dress that isn't white indicates that when you marry that you are not a virgin...This is generally frowned upon in the church.Regardless, colored dresses are becoming a little more popular again so as long as the dress color isn't an indication of your so called "purity", the priest shouldn't mind. I would ask your priest if your church has wedding dress color restrictions although I imagine that most do not.There is a lot of information on the origins of wedding dress colors at the link below... it is a long article or I would copy and paste.
http://www.wedalert.com/content/arti...Traditions.asp