There are many theories appearing in social media about orbs along with incredibly vibrant photos of orbs taken by ordinary people in ordinary locals but: I believe Orbs are angelic presence with the exception of the colour black which it seems to me that a negative spirit its bringing its influence too any particular area it appears in. Of course it may be that a bad incident has occurred involving that spirit when it was on the earth plane and it hasn't moved on to the higher levels where our loved ones dwell. Or it could simply be a negative energy that likes to cause disruption and stay around the earth on a psychic plane closest to the area it once knew.
ANGELICS AND ORBS
I believe that Archangel's have certain qualities that resonate with certain colours and thus the energy centres within our own body structure can be influenced by their presence:
White = Divine presence
Violet = Spiritual knowledge
Blue = Protection, communication
Green = Healing and source connection
Yellow = Beauty solar plex vibration
Orange = Relationship sacral vibration
Red = Base human quality presence
All of the above can be illuminated upon or reduced and even balanced by practising therapies such as Reiki, Yoga and Spiritual Meditation helping us live better lives and influencing healing and spiritual knowledge to those around us. It is all there for the asking say the Angels, Guardian Angels, Archangels, Guides and Ascended Masters who have all proven this to humans on earth over and over again through history to the present day.