Sauh (सौः) is para (परा) the infinite. It’s combined Shiv and Shakti beeja as colon(two dots). She represents the पद दवयं-combined Shiv Shakti. रक्त(Red-Devi’s Light) शुक्ल(White-Shiva’s light) मिश्र (conjunct) – Means Devi’s red light and Shiva’s white light conjunct as “Sauh” seed.This light only seen when Sauh sound is vibrated enough to release the light from Sahastrar Chakra on the crown of the head. Red-White light also represents Ardhanarishwar as a Guru.
Source: Discussion with Rakeshbhai Vyas UK.