worn by the bride
while being wed
Traditionally brides wear white or off-white, at least for a first marriage, although in some cultures, brides dress in red, green, or black.
The color white is considered to be symbolic of purity, but perhaps the original meaning of white, joy, would be a more appropriate symbol in a world where chastity is becoming increasingly less important. Attributing that virtue to any bride who wears white (or only to brides who wear white) is quite presumptuous, anyway. Many brides wear white despite their prenuptial adventures, and some women who have every right to bedeck themselves in the color of purity choose not to because white is simply very unflattering to them.
With non-traditional weddings becoming commonplace, any color or style of wedding dress is usually deemed acceptable. In fact, for many women, the chosen clothing to get married in isn't even a dress.
Thanks to the Reader's Digest book, Stories Behind Everyday Things, for the original symbolism of white and colors worn by other cultures.