Wow, I'm impressed with your precision. Two weeks ago I boiled annato seeds to add some color to a farmhouse cheddar, but I didn't take quite the care in preparing the decoction that you did, Boofer. The quality of the end product was therefore more coarse, I'm sure, but it seemed OK for use in a rustic farmhouse cheddar.
I placed two Tbsp. of annato seeds in one cup of water and boiled it in the microwave at two minute intervals for 8 minutes. I wish I'd started with a larger bowl as the fluid boiled over a bit at the first interval. I didn't cover the bowl figuring a little evaporation might concentrate the elixir. The liquid wasn't very dark, so I mashed up the seeds a bit with a spoon. I only strained through a medium wire sieve, so there was some fine particulate matter in my finished liquid. I had a little over 1/3 cup. I added this to the milk just before adding the rennet.
It gave the pressed cheese a light salmon pink color. There was some obvious fine granularity. I suspect that was from both the annato particulate (darker) and the slight coagulation of from the starter taking the dye differently (lighter) than more fluid milk. Different, not an unpleasant look, but rustic.
I tasted a drop of the liquid before adding it and found it quite bitter, so I didn't want to add more this first time trying it. I'd never used annato in cheese making before.
I'll be very interested in your results, Boofer. I'll try to remember to take some pics when I handle this cheese next, I've already larded it.