Dk; yes this should work for the cape.
ides; chestnut ink does work but brown works much better. purple ink works nicely too but the final effect will be a bit different.
erus; to get this deep red all over just extend the red/black mix to cover the entire armour plate and add another highlight stage of red and the tiniest drop of dwarf flesh right after the main red coat. clear as mud right?
i'll try to get something up to this effect later.