The Red Mage

     The Red Mage at its simplest is a combination of a Black Mage and a White Mage.  By utilizing both of these magic types, a team of adventurers could reduce their numbers by having a Red Mage on the team.  Not only can they heal and deal elemental damage, but their choice of equipment is much broader as well.  Unfortunately these mages cannot truly excel in either field of magic like their "pure" counterparts, but as far as being a "jack of all trades" sort of character, the Red Mage is a solid choice.
     Red Mages choice of weaponry ranges from staves and rods to basic military equipment like swords, rapiers especially.  This would allude to the idea that Red Mages are very dexterous beings, sharing some qualities with a thief as well.  While their weapon choice is better than that of the White or Black Mages, again, they can never truly excel at weapon wielding and must usually stick to the basics,
     Red Mages can also equip heavier armor than the other mages, another nod to their more active fighter role.  This does not mean that they have the level of defense that a warrior or paladin might have, but as far as mages go it can be very effective for them to be able to take more hits than the average spellcaster.
    Red Mages cast both white and black magic, but neither very effectively.  The idea with the Red Mage is to have a character that can do both very rapidly, constantly switching from one to another.  This can be effective in battles.  For instance a Cleric usually tried to avoid enemies in battle an wait for the need to heal to arise.  With a Red Mage, you would have a Cleric who would actually be able to output damage in the meantime, so no time goes wasted.  Obviously since the Red Mage cannot heal as well as a Cleric or deal as much damage as a Mage, it should definitely be up to the team leader to decide whether or not the team feels comfortable with such a gamble of a character. 
     The best course of action for a Red Mage would be to try to focus on one field of magic while only learning a little of the other in order to still be well rounded.  This way you could have a solid healer that still knows basic offensive spells, or an adept black mage that can still heal in a pinch.  The playstyle and usefulness of the Red Mage heavily draws from the ability of the player or leader to influence the mage to fit the team's needs.