You’re creating a dynamic material instance for each mesh, but then not using it ( see output pin ). It would work, if you did this and set the color on each instance as a vector parameter.
Problem with a material parameter collection will talk to all of them at once, that’s the point of it 
Even if you got the instancing working, they will still all set the same way.
Another, easier maybe, way to do it, is to have the same material on them all and use custom primitive data
