I haven't talked to anyone who has said there is a visual difference in het hypos, but I did notice one in Daytona that made me start asking the same question. I was looking for a female ghost and as I was walking around I saw one on a table so I walked up to see if it was a female, and it said that it was a het hypo male. It caught my attention from about 5' away, and just looking at it I would have sworn it was a mediocre looking ghost.