As mentioned R&K Salix, Platinum Blue Black, and KWZI IG Blue are good choices, especially if you want a bluish IG ink. Here is a comparison of the three:
Salix is well behaved (flow, feathering, shading are excellent), but the blue component is somewhat ethereal and will fade with time. Looks best using a wet pen.
Platinum Blue Black also is well behaved and somewhat bluer (blue component seems to be more permanent than that in Salix).
KWZI IG Blue #3 is much more saturated than the other two, and maybe not as well behaved as the other two in terms of flow.
Edited by MarkTrain, 21 June 2017 - 15:53.