How to I dynamically switch one texture in a ui widget to another?

So I’m trying to create a stealth game, in which a player is chased by a monster constantly and want to give feedback to the player on if the monster can see the player, when he can’t see the player this image is displayed on the HUD:

35793-monsteralertwander.png

And when the player is seen I want to display this image:

35794-monsteralertchase.png

I can get the idle green eye to appear when its a static material, but this doesn’t allow me to change the image and leaves me with an output that looks like this:

I supect that the issue could be one of two things:

  1. That I have made the base colour parameter the wrong type of parameter
  2. I am casting the dynamic material incorrectly

This is my Material Graph:

And this is the graph where I set the widget to the view port in the player character blueprint and material as dynamic:

Any help in this would be very much appreciated, thanks!