Question - How to set the default style on an MCQ?

I have a great custom template design that is set using the slide master and feedback master.

Most of the visual elements and positions of the content in each slide are controlled by the masters.... However, I cannot seem to find and set the default style for "multiple choice" questions. 

I can manually set the style for the buttons and rollover states, then copy that style using the "format painter" to repeat the styles for each question option but this method is ultimately flawed as any changes to states will mean after a style change is applied to the states I am unable to auto change all the states at once.

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My question is, how do I set / alter the default state of "multiple choice" inputs and apply that state to the slide master? See screenshot for specific element.

Any help would be appriciated.