When i was a kid, there was purple haze. Easily could of just been a haze strain with a purple pheno, or even just a guy calling his purple bud that.
Purple can be forced in some strains by dropping the temp shortly before cutting day.
Ive also heard stories about how p. Haze was a clone only strain. A weird pheno of a landrace strain from (insert random locale now) that was og far superior quality than even the best weed around.
Its amazing how a strain can sorta become a legend. Clearly those "legends" are bullshit.
If you want a purple haze, you could just pick your fav. Haze strain and force a few phenos of it purple to find the ones with the traits of it you want.
I never have bred any plants but the concept is simple.