ΔE 4.8, very close: most people won’t see a difference side by side. Dark Grey RLM42 is a little darker than RAF Extra Dark Sea Grey BS381C/640.
Yes, for most jobs. Very close match (ΔE 5). Dark Grey RLM42 is a little darker than RAF Extra Dark Sea Grey BS381C/640.
The same difference applies the other way round: RAF Extra Dark Sea Grey BS381C/640 is a little lighter.
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 RAF Extra Dark Sea Grey BS381C/640 on the colour wheel See Dark Grey RLM42 on the colour wheel
All matches: RAF Extra Dark Sea Grey BS381C/640 equivalents · Dark Grey RLM42 equivalents