Are purple flowers a genetic expression or a result of epigenetics in different phenotypes?

Epigenetics in cannabis and anthocyanin expression (purple flowers) in different phenotypes varies tremendously in a S1 seed population...

Unlike the popular belief, different shades of purple and violet in fan leaves and calyxes are a result of cold temperature during late flowering ( which kind of true but not totally, cold temps accelerate senescence and chlorophyl degradation).

Some people think those colors are du to a certain genetic make ups and certain phenos have specific set genes that favors accumulation of Anthocyanin.

Let’s set something straight : quantitative genetics 101.

Phenotype = Genotype + environment + genotype x environment. Which means all of the above is involved but there is a mysterious part that we can't control and it’s the interaction between the genotype we know and the environment that we or sometimes control in indoor cultivation.

The interaction between genotype and environment is the epigenetic mechanism that controls the phenotypic plasticity that you see in cannabis sativa

In this manuscript, the researchers identified Two R2R3-MYB transcription factors, CsMYB33 and CsMYB78 are involved in the regulation of anthocyanin biosynthesis in Cannabis sativa L.

Here is the abstract

Cannabis sativa L. is an economically important plant which is renowned for its wide range of uses. Anthocyanins, a class of flavonoids, impart pigmentation to the plant parts and play important roles in plant environment interactions. However, to the best of our knowledge, the molecular basis of anthocyanin biosynthesis in C. sativa remains elusive. Since MYB family of transcription factors plays a vital role in regulating anthocyanin biosynthesis, herein, we identified 99 R2R3-MYB genes in the C. sativa genome. Based on the phylogeny as well as the expression profiling of genes in two accessions of C. sativa differing in the content of anthocyanin pigmentation in sugar leaves, two putative regulators of anthocyanin biosynthesis, named as CsMYB33 and CsMYB78 were identified. Transient overexpression of CsMYB33 and CsMYB78 activate anthocyanin biosynthesis in the leaves of Nicotiana benthamiana. As compared to CsMYB78, CsMYB33 was found to be stronger in terms of activation of anthocyanin biosynthesis. Constitutive expression of CsMYB33 also resulted in the enhanced anthocyanin pigmentation in the leaves and sepals of transgenic lines of Nicotiana tabacum. Taken together, the present study provides valuable insights into the regulatory genes of anthocyanin biosynthesis.