There are several different theories that may explain the color differences in orbs…
Theory #1 – Color difference in orbs is caused by "chromatic distortion" which is a fancy way of
saying that our eyes perceive different wavelengths and shapes as varying colors. If a particle happens to be of a certain
makeup or shape, it will tend to absorb certain wavelengths of light and reflect others, thus giving the perception of a certain
color. Paravision has an interesting page on the anatomy of an orb.
Theory # 2 – Orb color difference is caused by the energy of the spirit who is represented by the
orb. For example, some ghost hunters believe that red and orange orbs represent a spirit who is angry or in need of healing.
Other shadow chasers claim that red is a color associated with an energy that seems to be on guard duty (often watching over
a last outpost, or a loved one who has died).