Ken's Original Granddaddy Purple help

Hello ,
I have one female Ken's Original Granddaddy Purple that is at day 40 of flower.

It is in 5 gallon bucket of coco / vermiculite. feeding with American hydroponics line.
600w HPS. Temp: 68deg night , 80deg day. 12/12.

They plant looks great , nice colas forming , lots of crystals , smells great , but no purple color except in the stems.
I thought Ken's purps had the genetics for the purple color.

I have read that while flushing the last week to bring temps down to 50deg at night to get buds purple , but I have also
read to increase the P/K in weeks 5 and 6.

Anyone grown this strain before and know why it is not showing any purple yet?

Thanks

Cooler temps will trigger color change. and not every pheno will have that trait

What does phenotype mean?
Sorry , noobie.

I also though Ken's Original Granddaddy Purple has the "purple color" gene already.
I thought phenotype was an trait outcome based on the plants genes and environment?
Thanks

I always think of kids when I try to explain phenotypes to my lady. Think of it as a set of twins. Some are identical. They share all of the same traits. They are just as tall as each other, look exactly alike, same eye color etc. Now think of paternal twins. They still both came from the same mother, and have the same genes. Yet they can show major differences. One might be taller, one might a dude even. I don't know shit about twins so don't hold me to any of those, it's just an easy way to put it.

Your not smokin it with your eyes man!

I wouldn't drop my temps below 55 just for color. You could end up reducing your yield. I've been growing purple strains for years and find it's the last 2 weeks of flower when you really see the color change. I believe your strain is a 8-9 week finisher. Which means it could take up to 10 weeks. Be patient i'm sure you'll get some purple going on soon. Good Luck!

A true GDP smoker knows that the best GDP isn't purple in color

Coincidentally I have some Ken's GDP that is at day 27 and is looking beautiful nice crystally nice kolas and is turning purple already. I keep my nighttime temps around 67-68deg. My experience with truly purple phenotypes is that they do not need cold. Purple is really just a color and it really is best to not attempt to dinduce a color change through deficiency or lower temps. Both will affect yoield and potency and the lower temps are just beggin for mold especially in a dense strain like GDP.

Don't worry about the color. People who love smoking gdp don't love it cuz its purple. I mean yea the bag appeal is nice but if its just personal smoke who cares as long as its fyah!!!