In the ritual at Somerton, the red worn by the Master of Ceremonies represents 'Satanic' forces, i.e., evil elite Jews, and the blueish-colored clothing worn by the two persons, one on each side of the Master, represents the 'evil feminine'. Kubrick believed that evil elite hermaphroditic Jews, highly-placed radical feminists, certain high-ranking Freemasons and Mormons, and other parties, are currently planning to establish a real-life, modern-day 'utopia' in the United States, in southern Indiana.
The black coloring of the cloaks worn by some of the guests at the ceremony, indicates that the ritual taking place has something to do with the alchemical nigredo stage, which is associated with, among other things, melancholia, and the encounter with the psychological shadow.[a] The ceremony participants represent persons who are, or who are associated with, the members of the real-life evil parties mentioned in the caption to the above screencap. The masks the participants are wearing symbolize the fact that the real-life evil parties are 'hidden' from plain view - they can operate 'under the radar', such that we don't see them for what they are: the source of much of the evil in present-day society.
Above left: When Bill gets home from the ceremony, he places a bag containing the mask and cloak he wore there inside a normally-locked cabinet, ostensibly so that Alice won't see them. Note the blue coloring in this scene - this indicates that an 'evil feminine' nature is present in the Harford household itself. Above right: When we see the mask on Bill's pillow later, this is an indication that Alice has access to the cabinet, unbeknownst to Bill.
Blue coloring is present even in the Harford bedroom. What is being suggested is that Alice herself is an evil feminine presence: She and Victor Ziegler have been leading Bill along the whole time - the entire sequence of events with Amanda, Marion, Domino, Nick Nightingale, and the others has been a plan being carried out; Bill has been set up. Part of the purpose of having him experience all the events that he does, is to get him to associate, deep within his psyche, the idea of philandering with the ideas of trouble and death, so that he will remain under his wife's control. Bill has been largely under the influence of his unconscious during much of the movie - either Alice and Victor are keeping him drugged or under some form of hypnosis, or he is, in fact, dreaming much of what we see; or, there is some combination of these. That Bill is being led along suggests that there is a 'hidden plot' in the movie; this will be discussed later.
a. Wikipedia, 'Nigredo'. Web, n.d. URL = https://en.wikipedia.org/wiki/Nigredo.
