Art is something that cannot be clearly defined to mean only one thing. Once "art" leaves its "creator," the creation takes on a life of its own becoming as unique as each person that interacts with it. This is my perception of what the story means.
"The Secret Room" was published by Alain Robbe-Grillet in 1962. The story seemingly presents a murder mystery; the villain is a dark-caped man; the naked woman—the "sacrificial victim"—is chained, dead. The woman has been shackled in a spread-eagle position, making sex with her not only possible but guaranteed—she would have been unable to resist. She is lying on a black velvet cover, thrown over purple pillows. The black cover is symbolic of death.
Purple has been symbolic of many things over the years: the Greeks saw purple not as a color but as...
...a sheen or iridescence, a mixture of light or dark on the surface.
This definition would allow that the purple might symbolize hidden depths or perhaps hidden meaning. Homer uses it to also describe blood. Shakespeare uses "purple" to refer to "gore." For example, in Richard II, Act Three, scene three, he writes:
...the purple testament of bleeding war.
On a more literal level, purple dye was so expensive that only "kings, emperors and aristocrats" could afford it.
In that the body lies on oriental rugs in plush surroundings suggests that this is not a place of penury but opulence and wealth. The murderer's clothing hints that he is not a common criminal. The room without visible boundaries symbolizes a situation that is widespread (not a singular event):
...this is not the whole room, whose considerable space must in reality extend all around...in every direction, perhaps toward other sofas, thick carpets, piles of cushions and fabrics, other tortured bodies...
The inability to pinpoint a light-source might indicate an event that is never displayed in the light of day, inferring this is hidden from the public eye. The presence of an incense burner may refer to the church. The woman's "milkwhite" body conveys a sense of purity or innocence. The man is described:
...a black silhouette...fleeing, a man wrapped in a long, floating cape, ascending the last steps without turning around, his deed accomplished.
The villain is "fleeing," and "his deed is accomplished." Later his face is described:
The man’s features are impassive, but tense, as if in expectation—or perhaps fear...
Based on these details, the dead woman may be symbolic of the loss of virginity: the death of innocence. The chains could imply marriage, and the incense, the church's blessing (which marriage would afford). The wound is on the woman's left breast, where her heart would be, suggesting that it was broken when the illusion of courtship and/or "feigned" love were destroyed with the "right of assault" that belongs to a man by virtue of marriage vows.
Mine is not a blanket statement regarding matrimony at all, but the idea of a woman sold into marriage with a lie. Specifically, the presence of wealth brings to mind the buying and selling of daughters/women based upon financial arrangements or the merging of upper echelons of society.
The man goes unmolested—"deed accomplished;" this might point to incidents when a woman is not joined in marriage by love, but with deceit and malice of intent—with social acceptance, as Robbe-Grillet might see it.
Ferber, Michael. A Dictionary of Literary Symbols. New York: Cambridge University Press, 1999.