If you wanna be a rat bastard, slap a Heal on the dragons list. Reds can also use cleric spells, so you should check those too. Especially because some Cleric spells are the same as Wizards, except at a lower level.
Divine Favor is also a good choice. And don't be stingy with the Protections from Elements. Cast against all 4 elements the dragon isn't normally immune to. Stoneskin isn't prolly a good idea, but maybe the dragon doesn't know that the whole party probably has +5 weapons?
Also remember following cleric spells: Death Ward, Spell Immunity, Freedom of Movement, Repulsion, Antilife shell.