Haldi ceremony is an important part of Hindu weddings. Haldi (turmeric) is considered sacred and applied both to the bride and the groom before the wedding ceremonies. All the family members participate in it and apply haldi in turns. So, you can expect to see yellow stuff all around.
Well, haldi is also considered good for skin and health in general. So, its health and fun hand in hand.
In this particular wedding, they had a small variation. So, you cannot find haldi being applied to the bride. On the other hand, they weave a thick rope (if I may call that) from a thread around the bride, which sort of represents the protection of the bride against evils. To me, it just gave a great shot. :)