My dragons are heavily based on D&D dragons as far as biology goes. They're 50-foot-long winged reptiles with, on average, human-level intelligence. This varies by subspecies, like with dog breeds, so that, for example, a white dragon is likely to be much less intelligent than a red dragon. All dragons, regardless of colour or age (beyond the first few years), can speak and read Common as well as Draconic.

There are 10 different varieties of dragon, each a different colour. While they can interbreed, the resulting offspring is always the same type as one of its parents, never a mixture. Each different type has its own unique abilities and preferred habitat: green dragons prefer forests, black dragons prefer swamps and silver dragons live in the mountains, for example.

Fire is the most common breath weapon for dragons, but it's still only possessed by three or four of the ten types (I can't remember right now). The others all have various other elemental breaths.

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