Liber XV, the O.T.O. Gnostic Mass specifies two officers called Children; these need not be (and usually are not) minors, the roles can be filled by any baptised member of E.G.C. (since we are all children of somebody, regardless of our age).
They are referred to as the Positive Child and the Negative Child. They are not the Fire Child and the Water Child, nor are they the White Child and the Black Child. Just Positive and Negative, since they represent the basic polarity of forces emerging from the ritual.
They both normally dress in white robes with black sashes, stoles, or belts. In the past some O.T.O. bodies would dress one in white robe and one in a black robe. However this was based on a misreading of the text of Liber XV.
The text of the rite shows that each officer is dressed in white plus another colour:
- The Priest wears white plus red
- The Priestess wears white plus blue & gold
- The Deacon wears white plus yellow (red, blue, and yellow being the three primary colours)
- The Children wear white plus black (the combination of all colours).
Verification of this can be seen if you read the text of Liber XV closely. It states “The Children [plural] are in white and black” and then it states that one carries water & salt, and the other carries fire & incense. In other words, they are treated individually only after the specification of their robes. So the implication is that each one of the Children wears white and black.
Note that this also corresponds to the practice of the 19th century French Gnostic Church, wherein the Deacons (who served a similar role in Mass as our present-day Children) wore white robes with black sashes.