Although the word 'demon' originally came from the Greek word for 'deity', for many hundreds of years it was taken simply to mean spirit. In the modern day it is taken to be an evil spirit, one at odds with God, and has this meaning in dreams. Psychologists now believe that demons in dreams are often personifications of deeply held or ingrained fears. The colour of the demons will often give information as to their relevance. Red indicates extreme and black might represent fear. Passionate beings with their own agenda, demons may represent a particular type of personality that will not allow itself to rest until a task is completed. You might like to consult the entries for Colour, Devil, Fiend and Imp.