I have a couple of variables set in place (vIdentifier1 and vIdentifier2). What I would like to happen is that when the user activates the button that sets vIdentifier to 1, I want vIdentifier2 (a seperate button) to have a low transparency. The two variables can't be set to the same value at the same time.
Use Rubens solution to manipulate the colours but to expand, you'll have to create the variable in the Variable output (Ctrl + Alt + V) or Script Editor and add an action to each button (External - Set Variable) i.e. vIdentifier1 = 1 vIdentifier1 = 0.