Master, what are the black [as purple], white, yellow and red colors that often appear in the text of Alchemy?


These are the colors which the Mercury displays when one is purifying the bodies in the crucible. What crucible are we referring to? The sexual crucible, of course.
In the beginning, this crucible emits a black color, then later, a white color. Subsequently, the yellow color is emitted, until finally reaching the red color.
This is the symbolism of the three Wise Kings: One black, one white and the other yellow. However, the red is missing. The red is missing because the Kings can only elevate themselves through the red color [sexual fire], the star that guides them is precisely Stella Maris. She guides them in the work. She is the one who performs the whole work. - Samael Aun Weor

In Jeremiah, chapter 21, verse 8, it is written: “Behold, I set before you the way of life, and the way of death.” Man and woman can use sexual intercourse and the delights of love and kisses in order to become Gods or demons.

From the dawn of life, a great battle has raged between the powers of light and the powers of darkness. The secret root of that battle lies in sex.

The correct interpretation of the mysteries of sex exists. The white magicians never ejaculate the semen. The black magicians always ejaculate the semen. The white magicians make the igneous serpent of our magical powers ascend through the medullar canal. The black magicians make the snake descend towards the atomic infernos of the human being.

Gods and demons live in eternal struggle. The Gods defend the doctrine of Chastity. The demons hate Chastity. In sex, the root of the conflict between Gods and demons is found.
-Samael Aun Weor, The Perfect Matrimony: The Great Battle