Spectrum Blue vs Great Hall Grey

How close are they?

ΔE 11.3, fair: the same colour family, but not a straight swap. Great Hall Grey is a little lighter than Spectrum Blue.

Can I use Great Hall Grey instead of Spectrum Blue?

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

Can I use Spectrum Blue instead of Great Hall Grey?

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

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.