Shane_The_Reader
Sorry this is so late and you may either not care or already know why but if not, here you go. Until the end of Shippuden, the highest gate Might Gai has ever opened is the 7th gate. This causes the user's chakra to grow so much, that chakra is literally coming out of their skin and creates a blue aura around them from pure chakra. Doing this in some unknown battle, Might Gai was given the title "The Blue Beast of Konoha."