Do you have a photo of the cygnet that you can send us? We have seen some really dark cygnets, but around 5-6 months of age, their feathers under their wings will start to turn white and then the rest of the swan will turn the eventual white of an adult swan.

If he is really dark, it just may be a color variation, but he should begin to turn to his natural white color in the next few months. The Regal Swan