Purple haze didn't die out because it wasn't all that potent, the seedbank that created the strain was destroyed.

There is an original haze strain that still exists and very rarely (every one in one thousand) a plant will have a purple color -- and yes the mutant is less potent.

There is a new generation of haze's on the market and you can get extremely potent haze. There are some really strong cultivar's in NYC, the variety of haze's you can get is incredible. While there isn't purple haze from the '70s anymore, there certainly is newschool purple haze (the buds wont be purple).

All haze's have a very similar smell and taste, so that is the biggest deciding factor in if what you have is real deal haze. The "purple" doesn't mean anything.

Sour diesel doesn't taste bad (think skunky sweet candy) and purple haze, errr, haze doesn't put you to sleep.