RAF Dark Sea Grey BS381C/638 vs Uniform Grey

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Uniform Grey is a little lighter, more saturated than RAF Dark Sea Grey BS381C/638.

Can I use Uniform Grey instead of RAF Dark Sea Grey BS381C/638?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Uniform Grey is a little lighter, more saturated than RAF Dark Sea Grey BS381C/638.

Can I use RAF Dark Sea Grey BS381C/638 instead of Uniform Grey?

The same difference applies the other way round: RAF Dark Sea Grey BS381C/638 is a little darker, more muted.

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.