Mechanicus Standard Grey vs RLM 74 Dark Gray

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. RLM 74 Dark Gray is more muted than Mechanicus Standard Grey.

Can I use RLM 74 Dark Gray instead of Mechanicus Standard Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). RLM 74 Dark Gray is more muted than Mechanicus Standard Grey.

Can I use Mechanicus Standard Grey instead of RLM 74 Dark Gray?

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.