Grey Blue vs Sombre Grey

How close are they?

ΔE 7.0, close: similar, with a visible difference side by side. Sombre Grey is a little darker, more muted, warmer than Grey Blue.

Can I use Sombre Grey instead of Grey Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Sombre Grey is a little darker, more muted, warmer than Grey Blue.

Can I use Grey Blue instead of Sombre Grey?

The same difference applies the other way round: Grey Blue is a little lighter, more saturated, cooler.

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.