Vertex Paint complicated materials? (i.e. 4.26 water)

I’m trying to vertex paint an algae material over water but I’m struggling to do so with 4.26’s’ new water material.

All the tutorials I’ve seen for material-blending involve either A. multiple textures + “VertexColor” or B. using “material attributes” + “layer blend”, both of which require actual texture samples. I’m curious how this would be done for something like 4.26’s new water plug-in’s material which isn’t as simple:

Currently, I’m using 2 planes stacked on each other but the result is poor and requires me to not use any waves else the water clips through the stationary algae: