I would not be afraid of clashing with the bride if you wear a colorful kilt. In the pictures I've seen of Indian weddings, the groom and other men were wearing colorful clothing, too. Blue does not clash with red, but ask the bride, and perhaps some older members of her family; wearing grey or another dull color to a wedding might be considered insulting.. You're blending traditions, so why play down the kilt. Besides, if she wears a dress anything like the one in the picture, she will be the center of attention, no matter what you wear.