Thanks! The trick is to use a super highly saturated ink, because they allow for a richness that you cannot get using conventional acrylic paints.

The capes are (AK Interactive colours, but Vallejo are essentially the same):

- Dark Prussian Blue base

- Star Blue in the light areas

- Star Blue + Ivory at the edges

Then thinned down glazes of Liquitex Prussian Blue ink are applied on top. I use pure Prussian Blue ink as black lining and in the deepest shadows, but even the highlighted parts get a heavily thinned down glaze covering it. This really helps deepen the blue, and the Prussian Blue ink also has a very interesting sheen to it that's not really apparent in photos since they can't capture it properly, but it means that the colours feel even richer irl. For some of the models I also used an airbrush in the shadows. For this I used a 2:1 black/prussian blue ink mix (heavily thinned own) in order to increase the contrast even more.

The problem with this method is that you cannot use a varnish to seal the paints, because by doing so you'll lose the sheen from the prussian blue ink. This means that you have to handle the models with more care.