You need a variable reference to the mat inst in dynamic form otherwise you can’t change the parameter values on the fly during game play so we must first make a dynamic version and to keep us from having to do that on tick we set it on begin play so it only fires once. The set material node makes sure that the new dynamic version of the material is applied to the static mesh on begin play then using the set vector values we are now setting the Color parameter values of the dynamic material in real time during game play…make sense?