To dream of a head represents intellect, attitude, personality or perspective. What guides your choices.
To dream of a head being cut off represents attitudes or perspectives that can no longer control decisions. Evil people losing their heads represents negative thinking patterns such as fears or bad intentions that no longer have any influence over you.
To see a blue head in a dream represents positive choices and decision making.
The head differs from the brain as a symbol in that the head is more about personality and the brain is about processing and figuring things out.