Material Colour is Not Updating on Clients

I have this in my GameMode BP, it sorts through the array of player controllers and then changes their pawns material instance based on their order to give them different discernable colours. However, it’s only visible on the Server.

I thought that everything in GameMode automatically replicates? Or because I am casting to character do I need to send an RPC back or something?

I found the answer to this. I changed the material instances to store as an array on the character, made a replicated variable called index and assigned each player controller their index base on the list.