Ooohhh.... time to google!!!
Basically a hardier version of the yellow. The
specs of 900cca, 75ah, 155rc are the same. The internal resistance is less than most batteries at half their output..... A tad heavy as they are lead coiled ...But the blue is a marine rated battery which means high cranking amps and deep cycle capabilibty with an excellent heat resistance, very high vibration resistance, faster recharge, can even be fitted upside down!
Not according to the Vbat site: according to them the Blue top have a CCA of 785 and 50amp/hr, as opposed to the Red top at 815 cca.