Sexuality
For Kevin Spacey, the life force which suburbia can't repress is sex. And so, in his fantasies, Mena Suvari, his object of lust, floats on a bed of red rose petals, or soaks in a tub covered in roses. In their final, near-sexual encounter, a vase of red roses is evident.
Peter Gallagher's (The ‘Real Estate King’) bus stop posters have a red background, for he unleashes Annette Bening's pent-up sexuality.
For Chris Cooper, the psycho ex-Marine, red is both sexuality and also the assertion of individuality. When he kisses Kevin Spacey, Kevin's bright red car is in the background.
Rebellion
For Spacey, red also symbolizes rebellion (a.k.a. the assertion of his individuality), another uncivilized impulse. When he buys the hot-rod of his boyhood dreams, it is, of course, bright red.
Assertion of individuality
For Thora Birch, Spacey's dark-haired daughter in the film, red also is related to the assertion of individuality. When she storms away from the stilted dinner after telling off her parents, she wears a sweater with red flowers.
There's a scene with Cooper's near-catatonic wife, Allison Janney, where she's cooking. On the wall, hanging on a nail, is a red oven-pad. It flashes by fast. Is it heart-shaped? In any case, that's her soul hanging on the wall.
Transcendence
For Wes Bentley, the young man with intense eyes, red means transcendence, another force which defies the emotional and psychological strictures of suburban society. He shows Birch his video of a plastic bag dancing in the wind as an example of the mystical continuity behind all life.
The wall behind the bag is red. Red also reappears as transcendence when Kevin Spacey dies. Though he has bled profusely, there's a slight smile on his dead lips. And his voiceover lets us know he's reached a kind of Nirvana.
Conclusion
Sex -- the assertion of one's individuality -- transcendence - and the soul -- all are examples of the life force. For some of the characters, the life force leads them to freedom; for others, not.
