This chart gives a rough idea of the colours, though some seem way off. My Minitaire colours are in numeric order if you want to compare them to the chart for names, the dark reds are: Innards, Regal Red. Nebula red is a decent darkish red (especially over a black undercoat) that I'm probably using as a base for my Blood Ravens, with Angelic Blood (very orangey) used for highlights.
Dark blue would be Nautilus Blue or Royal Blood which is really dark.
Another option would be using the Ghost tints over dark basecoats as they're transparent paints.
WGC and
OrcPainterNerd have done good videos showing them. Les has done one with
ghost tint fresh blood that is particularly applicable.