Married in white, you will have chosen all right. Married in grey , you will go far away. Married in black, you will wish yourself back. Married in red, you'll wish yourself dead. Married in blue, you will always be true. Married in pearl, you'll live in a whirl. Married in green, ashamed to be seen, Married in yellow, ashamed of the fellow. Married in brown, you'll live out of town. Married in pink, your spirits will sink."
In England (and thus spread over to the USA), wedding dresses only became white after Victoria married Prince Albert.
In some German regions, wedding dresses were dark even in latest times:
photo from a GDR magazine, 70's (I would say)
A wedding at about 1910 in the Black Forest