Hi, no, not tobacco mosaic! That’s sun burn! I had a strain that where exposed to the light, the leaves would turn black/purple!
Simply put, cannabis can turn purple due to high quantities of a compound known as “anthocyanins”. ... Anthocyanins are a water-soluble compound which is present in some cannabis strains. The compound can turn the cannabis leaves and buds into a variety of purples and blues which may even appear dark green and black.