ΔE 5.4, very close: most people won’t see a difference side by side. 3B Russian Green is more muted than Mechanicus Standard Grey.
Can I use 3B Russian Green instead of Mechanicus Standard Grey?
Yes, for most jobs. Very close match (ΔE 5). 3B Russian Green is more muted than Mechanicus Standard Grey.
Can I use Mechanicus Standard Grey instead of 3B Russian Green?
The same difference applies the other way round: Mechanicus Standard Grey is 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.