Brush color binding not working

Hi, I have this green border box in my widget that i want to change its color (from green to red) when certain condition is met. As you can see on the picture, i did a binding od the border box parameter “Brush color” and on the other picture you can see how i am doing the color change. In-game resault is that it will not even display the border box at any condition.
How can i efectively change color of that border box on a certain event in my 3rd person char.
Thanks for your help.