There are many speculations as to why the rooms are described in the colors and order that they are. My point of view is that they represent the stages of life. Blue (first) is the color of the unknown and represents birth - the very beginning. Next is Purple - the color of vivacity and life - this is the start of life and knowledge. Green comes third and represents the spring of life - growth. Orange, fourth in line, is the summer and autumn of life - the climax or height of life. Thus begins the decline. White is the winter of life and represents age as we think of white hair and bones. Violet is a shadowy color signifying the end as purple (life) is draped in grey shadows. Black, obviously, would then mean death - but the red window, the only window not in keeping with the monochromatic theme - implies death by the feared Red Death.
Several scholars have given a diversity of meanings to this question, but one of the most accepted ones is that the seven colors represent stages of insanity. Some others say they represent stages of life until the Prince reaches the last room, which is when he ultimately died. But for sure, as u see the progression of Prince Prospero from room to room, you realize that he is getting increasingly uneasy, and is about to lose his mind. The colors are blue, purple, green, orange, white, violet, and black (the color of mourning, and death)