Many of my friends keep asking me this questions. In India, white colour is usually associated with mourning. In traditional Hindu funerals, white is the standard Color for grieving friends and family members of the deceased. White is worn during funerals in India.
White has become the default wedding dress color for Christian brides. White is associated as being bridal and a woman in a white gown is instantly recognizable as the bride. You're free to wear any color you want, of course, but you'll then likely have to shop outside of bridal wear.
The tradition of wearing white isn't even that old, really. It gained popularity when Queen Victoria of England married Albert of Saxe-Coberg in 1840, wearing a white gown to incorporate some lace that she owned. At that time, a white wedding dress was extremely uncommon, and not a sign of purity, but a sign of wealth -- for only very wealthy women could afford a dress that could never be worn again (cleaning a white dress was not so easy in 1840).
The tradition continues today in the form of a white wedding, though prior to the Victorian era, a bride was married in any color, black being especially popular in Scandinavia. Many people assumed that the color white was intended to symbolize virginity, though this was not the original intention. (It was the color blue that was connected to purity because Mother Mary is usually shown wearing a blue dress.)
It dates back to white symbolizing purity in a time when couples were expected to be sexually innocent when they married. Most women today in the world are obviously not virgins when they get married, but the tradition still sticks. The whole "off white" thing started as the choice for women who were not sexually pure at their wedding ceremony.
In India, brides usually wear red. The color red symbolizes:- love, commitment, strength and bravery in Indian culture. In Indian context, red is also connected to the rising sun. Besides, according to astrology, the planet in charge of marriages, Mars, is red in color. Therefore, Hindu brides are asked to wear red during the wedding proceedings since it stands for prosperity and fertility. (If there is any other reason you can share it in the comments.)
White symbolizes celebrations in the Catholic community. Even during festive mass celebrations, priests wear white. Like if you attend a Christmas mass celebration or Easter mass celebration you will notice priests wearing a white robe. In catholic community, purple and black usually symbolizes mourning.
