We're used to talking about the color green when we discuss marijuana - so much so that "green" has become slang for bud itself. Although strains actually express a much more varied range of hues, none, perhaps, is more remarkable than the dark, grape-like purple of strains like Black Cherry Soda, a hybrid strain named for both its fruity taste and grape-toned buds:
The signature, purple pigmentation in these strains is caused by flavonoids known as anthocyanins. Also found in blueberries, eggplants, red cabbage, concord grapes, and violets, high concentrations of anthocyanins also occur naturally in some types of marijuana. The color comes out more vibrantly when plants are grown in an acidic environment, or exposed to drops in temperature - much as leaves in some parts of the world change color in the autumn.
Breeders, too, have played a role in the growing prevalence of purple cannabis, coercing and selecting for the trait to ensure an eye-popping product. That being said, a great, grape-y colour doesn't always translate into higher potency, if that's what you're after: as Leafly warns, "a purple-blossomed plant exposed to cold temperature may actually produce less THC."