ΔE 3.6, very close: most people won’t see a difference side by side. Sapphire Blue is warmer than Space Wolves Grey. They are different kinds of paint: Citadel Space Wolves Grey is a one-coat contrast-style paint and Green Stuff World Sapphire Blue is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 4). Sapphire Blue is warmer than Space Wolves Grey. They are different kinds of paint.
The same difference applies the other way round: Space Wolves Grey is cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Space Wolves Grey on the colour wheel See Sapphire Blue on the colour wheel
All matches: Space Wolves Grey equivalents · Sapphire Blue equivalents