Project Hessdalens categorisation on their website:
1 - White, or blue-white flashing lights. They are usually high in the air, close to the tops of the mountains or even higher. Their lifetime is usually short, typical some seconds. Sometimes they have been seen for a minute, but seldom any longer.
2 - A yellow light, with a red light on the top. This red light can be flashing.
3 - A yellow or white light. This is the most common description of the Hessdalen Phenomena. This light can stand still for more than an hour. It can move around slowly down in the valley, stop sometimes for minutes, start moving again. The shape is often round as a ball. Sometimes there are other shapes.
4 - A black "object" with lights on. This has been reported several times in Hessdalen. Here you can see a picture of such a phenomena. It was Leif Havik who took the picture in Hessdalen March 18. 1982. It shows three lights on this "black object":
Here is a drawing made by one observer of a similar phenomena in Hessdalen. A "object" with a light on each end:
Arne Wisth makes an alternative organization in the book "The UFO-mystery in Hessdalen" from 1983:
"We can affirm that at least four different types of UFOs are involved:
1: "The observation-UFO" which is round or egg-shaped.
2: "The hat," which has the classic flying saucer shape.
3: "The bullet", which is pointed at one end and rounded at the other, that often stands still for long periods and also lands.
4: "The cigar" - which is large, perhaps a hundred meters or more.
Are we facing a single phenomenon with different behavior, or are we facing multiple, parallel phenomena?