I think it's really difficult to say. In order to know for sure, there would have to be some long term research done by multiple Chocolate breeders who pool their findings together. Until that is know, it can never really be stated for fact one way or the other.
I guess that would be my question to someone breeding a chocolate or other non-standard colored dog--What research have you done and what information have you found to ensure that the color variance isn't accompanied by health issues. They should have a credible answer, as should any breeder.
