Ok, just updated it and now I have some greyish-dark green grass nearby in one of my newer worlds.
Anyone else seen that?
Oh, it might be for a swamp biome thing as the trees nearby have the same thing going on.
It changes the colour of the water as well. Sadly, my main base in SSP has now become a hideous swamp when it used to be a nice vibrant green. I'm thinking of throwing some vines up and abandoning the place, pretend it was ruined in some horrible catastrophe.