I found this in the "appearance" section of BLU for FFV:

Blue Mages have a vaguely "superhero" look. Most of the costume is blue, with a cape and shoulder pads, a domino mask.

For some reason it feels really close to the Spiderman teaser. Also this:

It is the first utility job in the game, providing both offensive and defensive capabilities. Unlike most other spellcasting jobs, Blue Mages can wield not only the common spellcaster equipment, but also swords and shields, giving them more offense and defense than a regular mage.

This kinda hints at the idea of BLU possibly being a tank.