We really need more info here to be sure - but I’m going to make a few assumptions and explain how I would do it based on them
Assumptions:
You’re using a box collision in your moving actor
The objects you’re trying to change the material for are static meshes inside of actors.
If these are the case, then what I would do is use an interface - give it a function called “ChangeObjectMaterial” or something of the sort. In your actors that need their meshes material changed, implement the interface, and do the logic for changing the material on the ChangeObjectMaterial function/event
In the moving object with the box collision, do an onComponentBeginOverlap, and out of the other actor use a “does implement interface node” do a branch to check if the colliding actor uses the interface, and if so, out of the other actor, call “ChangeObjectMaterial”.