So! I got Soot Black. I'll prob post a picture when I get home in a few hours.
I was part of the looper group, and what I did to get out of it was try to eliminate what I knew would be the problem. I thought about how we all fed so many Berries to get it to the lower color spectrum and how blue is probably the culprit. I at first tried Red, because well it made sense with a starting color of Yellow, that Red level would be higher. This didn't work, and the loop continued. I then remembered feeding it many berries and plums (more berries though) which would bring my Blue level higher more then likely, and my Red actually lower then I had previously thought. If you look at the charts, Blue is the lower end of Soot black, and obviously Ink blue has it a bit higher then the rest.
I figured at this point, it was actually Blue that was the culprit. I knew my reds were low as I had tried lowering them to no avail. So then it was time to try and bring up the other two evenly and get my blue under. x2 Pineapples did the trick for this (plume change x2), and now I'm a proud owner!
To those looping, I really don't believe in RNG in this system. Your color levels are probably just tilted in some form. Try to figure out which level of color is higher then the rest, even them out and raise them to Soot Black levels. SE rounds off colors to push you into a color tolerance IMO, and dipping above/below a range in certain numbers most likely pulls you out of certain pigments. Soot black's fairly even numbers probably just exacerbates this.
I really think this rounding is evident in how we are going from Ink Blue > Kobold Brown. The point swing doesn't make sense. I really wonder (especially since I got x2 Plume change messages with x2 pineapple) if I had used a Pineapple at Kobold Brown, if it would have put me at Soot Black. Numerically looking at Kobold Brown it doesn't make sense, but going from Ink Blue > Kobold from x1 Pineapple doesn't either. Something was off in the numbers, and for me it happened to be Blue.