IA, I hope you don't mind me commenting here but as soon as I saw your post I thought of a Mudra.
Reason being,

Light red blood suggests oxygenated blood
Dark red blood suggests blood with little or no oxygen.( got rid of oxygen....in nostril?)
A Mudra as you know is the sealing off of one nostril, sealing off the oxygen flow from one nostril at a time.

I always find things come in riddles to be worked out. The fact that you were told to stop this may just be part of the riddle to stop the oxygen/air flow.

You've started back up the throat friction technique again and I wonder if this is just a little hint to help you along?