Falsche Verwendung:
https://www.youtube.com/watch?v=6e3dLMD7a58&t=3m28s
Original:
http://fireaviation.com/2013/05/07/maffs-training-at-cheyenne/
The larger tank with the blue dot holds 3,000 gallons of retardant or water. The smaller white tank is for compressed air (at 1,200 psi) which pushes the retardant out of the larger tank.
Wikipedia: Modular Airborne FireFighting System