The pics aren't the best for studying confirmation. You really want a side long picture with the fish in a full flare. The first thing I noticed is that his anal is long which can be somewhat hard to correct, make sure if when choosing a female you pic one with moderate fins to balance out his anal.
The second thing is that his caudal doesn't appear to be even but then again he's not flaring and the pictures are at an angle so it's hard to tell for certain.
Here's a good article explaining what to look for in an HM.
Also a word about color. He isn't actually "purple".. he's a dark bodied bi color with blue and red which makes him appear purple... the genetics however are not going to give you purple. If you breed him don't have high expectations of getting tons of purple babies. You'll get a variety of multicolors, greens with red wash, etc. IME most fry end up favoring the mother as far as colors go.