I think you have MPCs back to front
They are for when you want to control a lot of material instances with one parameter.
Dynamic material instances, are for when you want to have parameter control over each instance individually.
I took the weekend off so I’m just now getting back to the project. I just watched a video on Dynamic Materials and this is clearly the proper solution to the gems themselves. After I got a grasp on the concept, I went back and implemented the BP code in your screenshot. It works on the gems! Thanks for the help there. I totally get what you’re saying about MPC vs Dynamic Materials Instances now.
Going to watch the video you shared and look into Post Process Materials now and try not to get too intimidated 