ΔE 7.6, close: similar, with a visible difference side by side. Sapphire Blue is a little lighter, more saturated than Tanker Grey. They are different kinds of paint: Army Painter Tanker Grey is an opaque base/layer 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.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sapphire Blue is a little lighter, more saturated than Tanker Grey. They are different kinds of paint.
The same difference applies the other way round: Tanker Grey is a little darker, more muted.
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 Tanker Grey on the colour wheel See Sapphire Blue on the colour wheel
All matches: Tanker Grey equivalents · Sapphire Blue equivalents