In Tibetan spiritual practice, for certain exercises, we visualise three light channels running vertically through our body. The central one connects the groin with the crown; the two lateral ones start at the nostrils and connect to the central channel in the navel area. The picture below should make this clear.
Each channel has various attributes and connections:
Right channel: Red, solar, male, fire, bile, snake, anger/ill will
Central channel: Blue, neutral, wind, wind (as a "humour"), rooster, greed/attachment
Left channel: White, lunar, water (and earth), phlegm, pig, delusion/confusion
Some of you already familiar with this scheme may have learned it with some of the attributes reversed. That's because there are different schools of thought on this. However, I believe that the scheme presented here is the correct one. Not that it would matter too much in practice, where your intent generally outweighs the details of your visualisation anyway.
In this topic, let's talk about that scheme and see what it can be used for.