The variety is named chocolate, regardless of whether it is created with the dun gene or with the choc gene. Serama carry both dun and choc, and many do not colour breed them, so knowing what a particular bird actually carries can be tricky. For other breeds, it partially depends on where in the world you are located. There are very few choc birds in the US other than serama. Limited numbers in wyandottes and orpingtons, and htat is about it. Other breeds with chocolate colouring are dun-based.