A little help for Greybar[sblock]From Tactics and Tips (Know your Enemy #9 and #11) in the WotC site:
I put in for brass and red dragons. You can extrapolate the below to use for other types of dragons.
Brass Dragons
The talkative brass dragon just wants to talk your ear off. Of course, if you don't let it, it's likely to gnaw your ear off instead.
Brass Dragon Lore
Characters with ranks in Knowledge (arcana) can learn more about brass dragons. When a character makes a successful skill check, the following lore is revealed, including the information from lower DCs.
Knowledge (Arcana)
DC Result
15 Brass dragons are good, loquacious, inquisitive dragons that live in desert areas. This also reveals the fire subtype.
20 Brass dragons can produce two types of breath weapons: a line of fire and a cone of sleep.
25 Brass dragons are immune to fire, but vulnerable to cold. They can speak with animals from birth. At various stages of its life, a brass dragon gains damage reduction: young adult -- DR 5/magic, mature adult -- DR 10/magic, very old -- DR 15/magic, and wyrm -- DR 20/magic.
30 At various stages of its life, a brass dragon gains the following special abilities: juvenile -- endure elements, adult -- suggestion, old -- control winds, ancient -- control weather, and great wyrm -- summon djinni.
Here is for red dragons:
Red Dragons
As a general rule of thumb, a DC 15 check or higher will reveal all of the base creature's type and subtype traits as defined in the glossary. This often includes information about energy resistance or various immunities. For instance, a DC 15 Knowledge (arcana) check reveals that dragons have high hit points (12-sided HD), all good saves, and have darkvision out to 60 feet and low-light vision. They eat, sleep, and breathe.
Information specific to the creature, such as its type of damage resistance, spell-like abilities, or immunities come with the high DC check results.
The red dragon is the baddest of the bad, combining brute strength with the sheer, terrifying power of its mighty fiery breath weapon. Most players forget that red dragons possess some unusual special abilities that seem outside the scope for such a fire-centric creature. If a red dragon wants to find you . . . it will.
Red Dragon Lore
Characters with ranks in Knowledge (arcana) can learn more about red dragons. When a character makes a successful skill check, the following lore is revealed, including the information from lower DCs.
Knowledge (Arcana)
DC Result
15 This also reveals the fire subtype.
20 The breath weapon of a red dragon produces a cone of fire.
25 Red dragons are immune to fire, but vulnerable to cold. At various stages of its life, a red dragon gains damage reduction: young adult -- DR 5/magic, mature adult -- DR 10/magic, very old -- DR 15/magic, and wyrm -- DR 20/magic.
30 At various stages of its life, a red dragon gains the following special abilities: juvenile -- locate object, old -- suggestion, ancient -- find the path, great wyrm -- discern location.[/sblock]