As a Breeder, we do get white puppies on occasion. While I do not agree that they are unhealthier than their colored littermates, they do have a risk of being deaf. Because of their white coat, they are more prone to sunburn which increases the risk of skin cancer.
No, they should not be registered, nor should they be sold at a profit. They do not conform to the breed standard, i.e. being more than 1/3 white. You can place them on spay/neuter contracts in pet homes. I am sorry that you have had trouble finding homes for your white puppies, as I always have people on my list more than willing to adopt them.
How old are they now? Do you plan to keep them, or are you still looking for homes for them? Either way, they need to be spayed or neutered.
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Cindy B/Copper Hill Boxers
http://www.geocities.com/copperhillboxers