Hello there,
you have to consider that Shadow blue is, in fact, more a really dark purple than a blue (I know, name is confusing

). I wasn't going for Soot black at all but Currant Purple

.
This was my journey which lead me to shadow blue.. Turning around it and being back to it, you'll see by yourself that trying to get a blue blue won't help you :
I decided to return to Shadow Blue after the last Charcoal grey.. You see how fast I went back to it.
I figure that might also help other people to achieve some other colors as I didn't saw any charts with charcoal grey, Mole brown or woad blue yet

.