Is feather color and pattern the same on both sides? He might qualify as a Mosaic.
There is not a drastic difference in coloring. His patterning may be different. I'll take a closer look today and if there is a difference I'll post some pics. He's starting to get a little tired of the recent increased attention though. He's been avoiding the camera this morning.
If he does cooperate for more pictures that will be really cool! I wonder if the color split is limited to his legs, or if he has white skin on some parts of his body and yellow skin on others. A chicken has yellow skin when it inherits the recessive allele from each parents for the color, making it homozygous for yellow skin. White skin is caused by a dominant allele. So if he has both colors on his body, there is no way for this to happen without him being a chimera of some sort, since the dominant white skin gene would be the expressed phenotype in a normal chicken.