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It can change the plants chemistry and make them flowers turn purple.

Is that why they call it purple Kush? Lol.

Yup! Not all cannabis strains can go purple. But Indicas tend to more often, and Kushes are mostly indica so that is how that works.

I am growing a strain called Vale Tudo Rd 1:

https://en.seedfinder.eu/strain-info/Vale_Tudo_Round_One/Copa_Genetics/

It has Kimbo Kush and Mendo Purples as its parents, so a good chance it will go purple if I can get the tent cold enough.

I see

yup.. and going purple changes the terpines inside the bud, shifting its flavor and possibly its high.