Adventures in juicing: part foam

Isn't this the most amazing colour? I just made another juice in my new juicer. Admittedly I have to take Gaviscon after most juices as they are too acidy for my stomach and it hurts, but I've not made a horrible tasting one yet.

You get a bit of foam off most- can you guess what's in this juice to create such wonderful coloured foam? Think green. Obviously.

The foam is the best bit. Or froth, I don't know if they are different things. I used to get to drink the froth off the top of my dads beer when I was wee. Before I developed taste buds and realised beer was awful. And my brother called it throth.