ΔE 9.2, close: similar, with a visible difference side by side. Mechanicus Standard Grey is a little lighter, more muted than Scarab Green.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Mechanicus Standard Grey is a little lighter, more muted than Scarab Green.
The same difference applies the other way round: Scarab Green is a little darker, more saturated.
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 Scarab Green on the colour wheel See Mechanicus Standard Grey on the colour wheel
All matches: Scarab Green equivalents · Mechanicus Standard Grey equivalents