I think you don't have a chance to click onto the traffic light directly. So try to use a button with a "Select in Field"-action. Your seach-field should be "Item" and your search string should contain the chart's expression (in single quotes!) which "turns the red light on".
Example for the searchstring to select all having sum(Val1) more than 4:
='=Sum(Val1) > 4'
So copy your expression from the chart into the serach-string like above and try it.