Ingmar Bergman does for the colour red in 1972's Cries and Whispers
what he did for black in his black and white films. Though there's plenty of black, too--the movie exhibits a predominance of black, white, and red creating the impression of volatile stillness, a tableaux violent and frozen.
We don't see a lot of gradation except in the few exteriors, most of which are tellingly flashbacks to when the four women who form the subjects of the film were happier, sharing a rapport strange for its ease and warmth compared to the frightened and wounded restraint that characterises their behaviour when most of the film's events take place.
Three of the women are sisters, the fourth, Anna (Kari Sylwan), is a servant who has been with the family a long time and her unflagging maternal affection for the sisters is emphasised in a variety of ways. Mostly in how Anna looks after Agnes (Harriet Andersson), who, bedridden with a terminal illness, is the reason the four of them are again staying in the same house. Also, perhaps, it's the explanation for the cold resentment forming between the other two sisters, Karin (Ingrid Thulin) and Maria (Liv Ullmann).
But, through flashback, both Karin and Maria are shown to be women with remarkably poor access to their emotions, in perhaps diametrically opposed ways. Maria is shown to have adulterous affairs with no compunction, and not displaying any concern upon witnessing her husband's suicide attempt. She's shown to have been spoiled by the sisters' mother, also, tellingly, played by Liv Ullmann.
Karin, meanwhile, in a pretty brutal scene, displays the lengths she's willing to go to to achieve the slightest level of notice from her negligent husband, who, like her mother, apparently prefers to bestow his affection elsewhere.
This, to be sure, is not the most radical story Bergman ever put together, but the visceral intensity of the four women's starkly coloured life in the house as they wait for Agnes to die is captivatingly horrific. It's mainly about the frailty of each character's coping mechanisms. Maria cracks under the stress of things not immediately going her way for once, Karin is so malnourished of affection she doesn't know how to give it, and Agnes, most incomprehensibly to the insensitive siblings, can't bear the strain of increasing physical pain. Only Anna's pain seems to be entirely based on her empathy.
After several movies fundamentally questioning religion, Bergman seems to find value in what is often purported to be an aspect of Christian morality--in the form of the deeply religious Anna who seems to be a never ending source of self-denying sympathy.