Dedicated server material change not working

I did set up a dedicated server with UE4 and got multiple clients (only 2 for now) joining it. I’m spawning a pawn from a GameMode class OnPostLogin:

and assigning the pawn’s ownership to the player state (because I did read that this should be replicated across all of the clients connected).
In the pawn class I’m triggering a change color event on the server (reliable and server only checked) as follows

But the problem is: I can’t see any change between clients. The SetMaterial calls are not being executed (or they’re being executed only locally, one player can’t see the other player’s pawn correctly colored and vice versa).

What am I getting wrong here?

How do you correctly propagate a color or material change to all pawns in a dedicated server?