Anthocyanins are the pigment responsible for purple hues, 💜 it functions slightly differently from chloryphyll or carotenoids in that its not attached to membranes its in the cell sap itself.
Anthocyanins are more stable and appear as red or pink pigments in acidic environments (pH 1-6). At neutral pH (around 7), they exhibit a purple hue. As the pH increases (becomes more alkaline), the color shifts to blue and then to greenish-yellow, and eventually colorless in highly alkaline conditions.
Looks like the dark green I'd expect from nitrogen excess but hard to tell.
I copy and pasted that last part :)
