Hi Adam
The red button is for service only... it allows you to take your car out of Park whilst the engine is off
The other two buttons is for kickdown... if you want your gearbox to change gear as soon as you boot down the accelrator then keep the button on Power, Norm is if you are on a freeway and you want to casually overtake whithout the car dropping down into 3rd.
Give it a try when on the freeway.. do about 50 then boot down.. you will notice the difference