Blue has been a staple color of the Dragon Ballfranchise for years now. Even though yellow and gold designed transformations back during the Dragon Ball Z days, Dragon Ball Super changed things when Super Saiyan God Super Saiyan became the most used form in the series. Even before Suepr Saiyan Blue was brought into the picture in Resurrection F, Dragon Ball already had a blue transformation (and it was one of the strongest SSJ forms in DBZ).
