Blue mage makes the most sense to me as well regardless of people digging into the game 3.5 files. A spider bit peter parker and he became spiderman. A blue mage gets hit with Beast magic and gains his powers. The samurai Sam Raimi theory is just too much of a reach IMHO. Blue Mage would also fit the Ala Mhigo theme of the Expansion.

There is also a red vs blue theme going on in Stormblood. even the name stormblood conjures image of blue and red. Storm = Blue (there's even a dye in game called Storm Blue :P), Blood = Red. Then we have the Trailers with the blue and red auras and the Azure and Crimson in the New Years Poem, even spider man himself has a red and blue costume.