Good observation, Roger.
I had forgotten about that 3D Butterfly weight illustration, showing a full green central section, which is probably overlaid directly onto the regular colour ground.
The main difference with my domed weight, though, is that the green is a "wrap-around" fill between the rows of canes. However, the powdered white does show as edging to the green and also to the inner/upper row of canes - but not around the central cane, which looks to be set on a fully clear section.
I also have a Salvador Ysart "Upright Flower" with a green inner ground and two rows of canes, looking like the base section of many of his 3D Butterfly weights. But in the flower weight there is no main colour ground (i.e. it is a clear ground), so the green section really is just a central layer.
These variations in ground styles extend the possibilities of collecting themes for Ysart weights. I wonder what we will find next.