Ok, let me have a crack at explaining this. This is a Central Bearded Dragon; there are no sub-species. If the previous owner has told you that this animal is a 'half yellow phase', then this simply means that one of it's parents was particularly yellow. You can see for yourself well enough how colourful your dragon is, but you might also be interested to know that your animal may be likely to produce offspring that are well...more yellow based on it's genetics. Hope that helps. Your dragon looks very nice, and is obviously well fed.