If you look at goku and vegeta when they fought Frieza during his resurection. They were not in their normal base state. They were in God-like saiyan state. The super saiyan form of a God-like saiyan is super saiyan blue, since Super Saiyan God and Super Saiyan Blue is only a 5x difference. Which makes sense, since their is no Super Saiyan 2 God-like saiyan or Super Saiyan 3 God-like saiyan forms. If you look under goku or vegetas' battles they only use this form against Frieza. They chose to use Super Saiyan God from then on.