Rani heard a Jeopardy question related to the following information the other night. This is what I found when I looked it up. . .
Because the Angels are incorporeal beings, though they nevertheless take on human form when appearing to mankind, it can be difficult to differentiate one from another in icons.
However, Gabriel is usually portrayed with certain distinguishing characteristics. He typically wears blue or white garments; he holds either a lily (representing the Theotokos), a trumpet, a shining lantern, a branch from Paradise presented to him by the Theotokos, or a spear in his right hand and often a mirror—made of jasper and with a Χ (the first letter of Christ (Χριστος) in Greek)—in his left hand.
He should not be confused with the Archangel Michael, who carries a sword, shield, date-tree branch, and in the other hand a spear, white banner (possibly with scarlet cross) and tends to wear red. Michael's specific mission is to suppress enemies of the true Church (hence the military theme), while Gabriel's is to announce mankind's salvation.
Taken from http://orthodoxwiki.org/Archangel_Gabriel