They can of any colors.
Their breath is a powerful weapon.
Most Common: Fire
Second Most Commons: Cold, Electricity
Rare: Acid, Poison, Lava
Extremely Rare: A breath that is a combination of other effects.
They never die from old age.
They tend to sleep a lot, sometimes for decades or centuries.
Endruil
This very rare red gold is produced in a thick layer on the inside of a dragon's egg when the hatchling breaks the shell.
Unless the dragon breaks it from the inside with his tiny nose horn (the only one to pierce the dragon's skin before it hatches) the inside layer of the shell will not transform into Endruil.
Reproduction:
No gender or sex.
All dragons can produce eggs.
To quicken an egg, it must be breathed on by a different dragon.
Size:
The egg is about 30cm tall.
They are born measuring one meter from tip to tip and tip to tip (snout to tail and wing to wing).
Their body is 1/3 their full length.
Growth Rate:
They grow one meter per year until they are 6m long.
Then 1m/5y they are active, until they are mature.
Then it's 1m/20y, until they are 25m long.
Then it's 1m/100y.
They rarely grow beyond 25m long, only the most powerful and ancient do.
They are mature at 10m long.
When they are mature, they can use magic and lay eggs.
A dragon can lay one egg per decade.