The short answer is that the blue kernels would be safe to eat. The pigment is most likely anthocyanin similar to what is found in blueberries and purple cabbage and does have various human health benefits when consumed regularly in large enough quantities. The blue kernels would most likely come from an outcross, but its not clear in which generation this might have happened. Blue would be dominant to white and if the trait is expressed in the endosperm, then its possible that an outcross with an ornamental corn – such as the questioner suggests – might have been the source. If the pigment is in the aleurone or pericarp layers of the seed, then its more probable that the contamination happened during seed production.