During my fascinating ghost hunting trip in Tennessee, I had a conversation with Steve from Southern Ghosts (http://www.ghosteyes.com/) about the colors of orbs. At that time, he told me to run away if I saw a green orb because they were often associated with evil. Of course, he could have been just pulling my leg. I was the new girl and who doesn't want to see if you can't play a little joke on the new girl, but I believed him. Whether he was pulling my leg or not, the entire conversation got me thinking about green orbs and whether orb colors have meanings. It did take me two months to research this, but here is what I found out about green orbs.
First of all, many people assert that orbs are standardly photographic error and can not be considered of supernatural origin at all. Others still insist, however, that orbs are an indication of the supernatural once photographic error has been ruled out. They insist that orbs are a way that ghosts manifest themselves. Assuming the later is true, we have to wonder why some orbs have different colors. According to www.moonspenders.com , orb colors have significant meanings and the observer can learn much about the nature of the haunting from orbs that deviate from the standard white color. These orbs are rare, but very significant. According to them, a green colored orb signals a friendly and communicative spirit. Coast Ghosts at http://www.coastghosts.com/ , agrees with this theory and says that green indicates healing.
Michelle Meyers of Ghost Hunting Secrets (http://www.ghosthuntngsecrets/) presents two theories on the colors of orbs. Theory one states that coloration in orbs is due to chromatic distortion and is simply due to our perception of light. Theory two states that the color of orbs is significant and can be used to interpret the energy of the ghost. Again, Meyers refers to a sight that interprets the meaning of green orbs as healing spirits. In fact, almost every site I visited that discussed the meaning of orb colors agreed that green was a positive color to see in an orb and red or black was more representational of negative and hostile energy. So what I learned from my research is, if the orb is red or black run away and if the orb is green, stay and play. The most common list of orb color meaning is below. I found this list at http://www.moonspenders.com/.