Is it possible to change individual point instances' material bindings in Solaris/Lops?

For example, I could have 100 spheres instanced on a grid using a point instancer. I would like to assign a separate material to each group of 20 spheres. The material:binding attribute on the instancer is not an array attribute like some of the others, I'm curious if there's a way to get around this

I've tried the "modify point instances" lop and the "material variation" lop. It could be user error as I haven't dealt with those before but I haven't gotten them to work. I think the material variation lop just allows you to vary a prim attribute which would work if I could vary the actual material binding per instance but I cannot...

Well I figured out that you cannot assign a material to specific instances IN THIS WAY. You can use the "edit prototype" LOP to basically "duplicate" a prototype and reassign it to a specific instance. You can then apply a material to this new prototype. For working with a large number of instances and choosing which one gets which material, python could be used to do this.