Color Change in Cannabis: How to Induce Purple, Red and More
Quick answer: Cannabis changes color mainly because of anthocyanins, natural pigments that produce purple, red and blue hues, revealed as chlorophyll fades. You cannot force color on a plant without the genetics for it, but with the right strain, cool nighttime temperatures late in flowering bring it out. Color appears most in leaves and is largely separate from potency. Pigment shifts are driven by genetics and environment, the same factors shaped by mycorrhizae at the roots and your outdoor watering routine.
Cannabis can shift from plain green into striking purples, reds, blues, even pink or near-black, especially late in flowering. The main driver is anthocyanins, the same flavonoid pigments that color blueberries and grapes. The plant already carries them (or does not), and they become visible as green chlorophyll breaks down.
Recommended Strains
Alaskan Purple
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THC | 15% - 20% (Medium) |
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Type | Feminized |
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Yield | Medium |
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Phenotype | 70% Indica / 30% Sativa |
Auto Purple CBD
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CBD | 17% – 19% (Medium) |
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Type | CBD Autoflowering |
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Yield | Low |
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Phenotype | 70% Indica / 30% Sativa |
The key thing to understand is that genetics come first: a strain without anthocyanin potential will never turn purple, no matter what you do. But in a strain that has it, the right environment, mainly cool nights late in flower, can coax out vivid color. The table below maps each color to its cause and how to encourage it.
| Color | Main cause | How to encourage it |
|---|---|---|
| Purple / blue | Anthocyanins (genetic) + cold | Purple genetics; cool nights late in flower |
| Red / pink | Anthocyanins in acidic conditions; some phosphorus stress | Red-leaning genetics; cold; slightly acidic root zone |
| Yellow / gold | Chlorophyll fading late in flower | Natural ripening; normal nutrient draw-down |
| White / frosty | Trichome coverage (not pigment) | Strong light; trichome-heavy genetics |
Genetics Come First
Genetics set the ceiling. Some strains are packed with anthocyanins and turn purple, blue or crimson with little coaxing, which is why names like Purple Haze, Granddaddy Purple and Blue Dream are famous for color. Choose a strain bred for it and you are already most of the way there.
It is worth setting expectations honestly: color usually shows most in the fan leaves, branches and sugar leaves rather than the buds themselves, so even ‘purple’ strains often keep green colas with flashes of color around them. A plant without the genetics will just stress or brown if you chase color, rather than turning purple.
Promos & Deals
How to Bring the Color Out
The single most effective trigger is a temperature drop. In the last two to three weeks of flowering, letting nighttime temperatures fall to roughly 50-60 F (10-15 C), while days stay warmer, slows chlorophyll production and unmasks the anthocyanins underneath. That day-night contrast is what growers use to push purple and red.
Light can help too, since more light exposure encourages pigment in some strains, and the natural cooling of autumn is why outdoor plants often color up late in the season. Avoid chasing color with extreme cold, nutrient starvation or stress, which harms the plant and yield for little gain. Work with genetics and gentle cold, not against the plant.
Red, Blue and Other Colors Explained
Different colors come from the same pigment family behaving differently. Anthocyanins tend to look red or pink in more acidic conditions and blue or purple in more neutral ones, which is why a red cannabis plant and a purple one can share similar genetics expressed under different conditions. Yellows and golds, by contrast, are usually just chlorophyll fading at harvest, not anthocyanins.
If you want to choose colorful genetics or understand specific hues, see our guides to purple strains, blue weed and the most colorful strains. For the popular cold-water myth, our ice water purple buds guide sets it straight.
Common Myths About Cannabis Color
A few persistent myths are worth clearing up. The first is that putting ice on the roots or shocking the plant with cold water will turn buds purple overnight. It will not: without anthocyanin genetics, cold just stresses the plant, and sudden shocks can harm it more than help. Gentle, sustained cool nights in a strain that already has the genetics are what actually bring out color.
The second myth is that purple or colored weed is automatically more potent or more flavorful. Color comes from anthocyanins, which are largely independent of cannabinoids and terpenes, so a vivid purple bud is not inherently stronger than a frosty green one. Choose genetics for the effects and aroma you want first, and treat color as a bonus, a beautiful one, but a cosmetic trait rather than a measure of quality.
FAQs About Color Change in Cannabis
How do you induce color change in cannabis?
Start with a strain that carries anthocyanin genetics, then drop nighttime temperatures to about 50-60 F (10-15 C) in the final two to three weeks of flowering. The cold unmasks the pigments as chlorophyll fades. You cannot force color on a strain without the genetics, and extreme stress harms the plant rather than coloring it.
Why is my cannabis plant turning red?
Usually anthocyanin pigments, which can appear red or pink (often in more acidic conditions) as cool temperatures reveal them late in flower, a normal, often attractive trait in strains with the genetics. Occasionally red stems or petioles signal a phosphorus issue, so check for other deficiency signs if the plant also looks unhealthy.
Does purple weed mean it is stronger?
No. Color comes from anthocyanins, which are largely separate from the cannabinoids that drive potency, so purple or red weed is not automatically stronger than green. Judge strength by the strain’s genetics and THC, not its color. Color is mainly an aesthetic and genetic trait revealed by cool temperatures.
Can you turn any cannabis plant purple?
No. A plant will only turn purple, red or blue if it carries the anthocyanin genetics for it. In a strain with that potential, cool nighttime temperatures late in flowering reveal the color. In a strain without it, cold and stress simply damage the plant rather than coloring it, so start with colorful genetics.
At what temperature does cannabis change color?
Cool nights of roughly 50-60 F (10-15 C) in the last two to three weeks of flowering, while days stay warmer, are the usual trigger in strains with the genetics. The day-night contrast slows chlorophyll and unmasks the pigments. Avoid extreme cold, which stresses the plant without improving color.
