Pastel Blue vs Sombre Grey

How close are they?

ΔE 11.1, fair: the same colour family, but not a straight swap. Sombre Grey is a little lighter, warmer than Pastel Blue.

Can I use Sombre Grey instead of Pastel Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Sombre Grey is a little lighter, warmer than Pastel Blue.

Can I use Pastel Blue instead of Sombre Grey?

The same difference applies the other way round: Pastel Blue is a little darker, 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.