That Purple Blimp is the only Bloon of Round 751, and it only appears if you beat Round 750. It has 2,000,000 health, 15 Auracrysts, 600 Aura Barriers, 30AD, moves at 0.4x the speed of a Red Bloon, regenerates 70HP per second, and is as large as your whole screen. It contains 5 F.R.A.X.Y.s and 200 Regen B.L.I.T.Z.s.