These lights are almost always blue, for reasons unknown. They are heavily described in folklore not just for their 'mischievous' properties, but for their mineral locating abilities as well. A good example of this fact can be observed in Bram Stoker's 'Dracula'. Dracula is seen to be locating something at the beginning of the book by 'blue vapours'. This points to a different type of chemical reaction, possibly the same type as used in bioluminescence.
Ball lightning is, as the name suggests, balls of lightning produced in a thunderstorm.
It usually occurs after intense flashes of lightning, and are usually described as 'balls of fire' 1-100cm large, and not usually lasting more than a few seconds. These balls have very similar properties to earth lights, except ball lightning tends to explode rather violently. They may have exactly the same process going on behind them, except that the power involved in ball lightning is much greater. Ball Lightning at this site. General introduction and theories.