ΔE 9.3, close: similar, with a visible difference side by side. Mechanicus Standard Grey is a little lighter than Strap Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Mechanicus Standard Grey is a little lighter than Strap Grey.
The same difference applies the other way round: Strap Grey is a little darker.
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 Strap Grey on the colour wheel See Mechanicus Standard Grey on the colour wheel
All matches: Strap Grey equivalents · Mechanicus Standard Grey equivalents