How do i get the Base Color parameter

after making the Thing a Parameter/Property in the material
then How To Change A Material Instance Parameter On A Blueprint Object? - #7 by Jacky

then you can modify whatever the parameter is, just be aware that this does increase overhead by technically duplicating the data for the given Parameter/Property to live in both VRAM and RAM, this can be mitigated a bit by Resizable-BAR, but you should still do this with moderation, or with a low number of materials being instanced (The GPU is optimized to reuse Geometry and Texture assets if they appear multiple times in the rendered frame.