You will probably have seen in the samples that the bulk is colored, but there are also black-and-white photographs. If some photos are delivered BW they have a reason that is black and white and can not be colored. However, you can ask for your wedding to have more than one type or the other, or if you prefer to be exclusively colored or black and white. If there is no specific reason why you prefer one or the other kind, better leave it to your photographer's judgment.