The root color patterns in face and fret tunics correspond with diagonal pathways produced in thread wrapping. Parallel diagonal pathways can be Z or S slant (left and center) and opposed diagonal pathways alternate in being S and Z slant (right).
Isbell, William H.; Uribe, Mauricio I.; Tiballi, Anne; Edward P. Zegarra, 2018, "Visual database", https://doi.org/10.25346/S6/1B33FN.