Ive grown my fair share of purple and pink strains and its all a roll of the dice with seeds. With clones you are getting the same genetics as the mother plant so the only variation comes from environmental stuff.
The purple strains ive grown wound up being 50/50 and the pink strains ive grown i havent gotten even the slightest bit of pink.
As far as purples go, if a strain is geneticlly predisposed to going purple, you can try to bring it out more by having lower temps. Dont go too low, but night time temps of like 65F has brought out the purple in some of the purples ive grown.
All in all while purple looks cool, i personally think the high on most purple strains is lacking a little in comparison to normal green weed.