The Red Dragon as commonly portrayed in fantasy fiction and role-playing games
The Red Dragon is generally considered to be the greediest, scariest, and nastiest of all the evil dragons. They are exceedingly vain, xenophobic, and are known to keep inventory of their treasure hoards right down to the last coin.
Baby red dragons have tiny bright glossy scales, which are highly visible in most outdoor surroundings. Because of this, they are generally kept underground until they reach puberty, at which point their scales become a duller, deeper red. The scales of a red dragon continue to grow in size and thickness throughout its life, which means that very old red dragons have incredible natural defenses.
Most red dragons prefer mountainous lairs. This allows them to look down over their domain, and generally pump themselves up about how mighty they are. They almost always live alone, unless they have children, or magically controlled servants. Other dragons are viewed only as competition, unless it is mating season.
Most red dragons attack anyone and everyone who approaches their lair, although they have a particular hatred of good dragons. They can digest anything, but tend to eat meat, and many of them have a taste for maiden flesh.
The red dragon is a terrible foe in combat, but they tend to be overconfident, which is something that can be used against them. Solo adversaries will generally be attacked by the conventional means of tooth and claw, while larger groups will be hit with spells and the dragon's terrible flaming breath weapon.
Your local red dragons may vary. I recommend consulting a local wizard or sage before making any dragon related decisions.