They, along with the dragon arrows, are technically not like other Dragon equipment in that they are not made from dragon metal and are therefore not red in colour. Rather, they are made from a dragon's talons.
Dragon darts are often used by pures in The Wilderness as they hit very quickly and deal moderate damage; a good way to PK with them is to throw three darts and change to a more powerful weapon such as a 2-Hander or Dark bow.
A better alternative exists to Dragon darts: Blisterwood stakes have higher damage and accuracy bonuses, and are free to make, however, they require more effort to obtain. Sagaies are slower, but have even higher damage rating and accuracy than the stakes, and are generally cheaper than the darts, but can be quite hard to buy.