On the literal level, Edgar Allan Poe's "The Masque of the Red Death" is a tale of terror that has as its setting a terrible plague that leaves red stains on its victims. The very wealthy and influential Prince Prospero, like the other residents of the area, fears the deadly disease. So, he and members of his court sequester themselves in one of his old castles that is a "strong and lofty structure" where they remain for several months. Finally, the prince decides to have a masquerade ball, a fete popular for his times.
Each room is decorated in different colors. Thus, each room represents a stage of a person's life. There are arabesque figures, representing the delusionary aspect of the room. The last room is decorated with black tapestries with red staining the windows. Recognizing the significance of the colors, the guests are afraid to enter the black room. This final chamber has another haunting aspect: a huge ebony clock strikes on the hour, causing the celebratory guests to pause. When this clock sounds twelve strokes, an unwanted guest enters this room himself, disguised with a heavy cape. Incensed that such a guest as the hideous one in the black cape should have the effrontery to enter his castle, Prince Prospero accosts him with his sword raised. Suddenly, the weapon falls to the ground, as Prospero has entered the room of death. He falls victim to the Red Death that he has sought to barricade from his and his guests' revelries.
As an allegory, Poe's story demonstrates how people react to their own mortality. The prince certainly feels that his wealth and material possessions can protect him while the guests seem to embrace the Roman motto of "Eat, drink, and be merry; for tomorrow we will die" as their revelrie only ceases as long as the clock chimes.
Literally, the story is about a man who comes into a party with a contagious disease that spreads and causes everyone in the party to die after one hour of exposure.
The story may have been inspired by the plague in Europe, during which splotches would appear on the bodies of the afflicted. in "Masque of the Red Death" splotches of red appear on the faces of the victims.
Color symbolism is also used in the story. The black and red room is the room where everyone dies, meaning that black and red are the colors that symbolize death, while the other colors may symbolize different aspects of life.
I think your interpretation of being unable to escape death as a theme or symbolic meaning is a valid one.