Darth Maul is easy to distinguish from all of the others listed above - red base, with splotchy black spots all over, even out on the skirts. Everlasting Gobstoppers should have a green mouth, and Goochsters should have a bluish disc around the mouth (not speaking from experience, but if its similar to the bluish disc on the PE zoas, it may disappear under bright lighting, so maintaining the blue may require shade). Devil's Armor and AoG can sometimes be confusing.
As Charles said, AoG (at least the old school AoG) is a bright vivid red which actually "glows" under actinic lighting, with striations extending out to the skirts, and I would describe the skirts as greyish to brown. That said however, I have had AoG that actually looked more pinkish than red.
Devil's Armor IME is almost always more on the pink side, with definite black spotching within the oral disc and grey skirts.
