Notice...all this is based on theory and individual study, but makes pretty good sense if you think aobut it....

Basicaly they represent other life forms, either once human or other creations that are in another dimension, one that we cannot see with the human eye, (Or most of us can't...smile.)  They are made up of the life force or energy that the being is living with at the present.  Think of the human body as a Tupperware container for the souls energy...once that 'container' is of no use and dies, the soul is free of it's earthly 'box' but because energy can never be destroyed, it continues onward and is eternal...(Of course we could get into some legnthy discussions on religious beliefs right now, but this isn't the place for it...go to Hannibal's Specters Basement Yahoo group and start a new message thread if you want to discuss this further.)  Some belive that the 'orb' is the simplest of shapes that matter can form, like bubbles.  When these ghostly orbs start forming into a recognizable figure of a person it means that the entity is actually pulling together it's mass of atoms to form a more denser image, or so it is believed. 

The coloring of orbs have different definitions also...they can reflect the entities mood, or temperature, or reflect the personality, such as white for good or pleasant, red for evil or demonic, yellow for adolesents, ...or so it's been theorized.

Below  is a fantastic photo filled with a variety of sizes and colors of orbs that showed up in the same shot that we captured during one of our investigations.