Orbs can be various things:

If you have headaches orbs can be the sign of a migraine so not spirit. Some sentient people see orb colours when they hear music or see words, again this hasnt got anything to do with spirit.

If you dont come under these, then coloured orbs can be a sign from spirit - I get an awful lot of cobolt blue orbs.

Colour has two trains of thoughts, some say all the meanings are the same for everyone, while others believe its an individual thing. For me and most in text believe purple is related to spirituality, but can also mean power of the church.

I feel the orbs are just a recognition just like touching us would be.