Change BP actor material by collision from other BP actor

Hello! In my 1st BP actor I have expanding object and and its collision. So when it overlap collision from 2nd BP actor, 2nd actor must change its material.
I think it must be realized by variables ad “cast to” node
But I am not sure I know what I should do
Please help!

you would do this exactly how you described it above. you would use an OnCollisionEnter Event, then drag out the Other Actor Pin and type Cast To (Blueprint name). then set the new material.