GW blue-grey for me, although mine comes out a bit darker after washing. The Studio paint mix was a 50/50 of Space Wolves Grey and Shadow Grey,
IIRC. Mine's a 50/50 of Fenrisian Grey and The Fang, with the dark blue wash to get into the crevasses. Highlights were Fenrisian Grey. I suppose I could base with the Fang, layer up with my 50/50, and then highlight with Fenrisian to get the same effect without a wash if I wanted.
Only real issue I have is that The Fang is a Base paint and Fenrisian Grey is a Layer (different pigment concentrations).