Great Hall Grey vs Sand Grey

How close are they?

ΔE 7.3, close: similar, with a visible difference side by side. Sand Grey is a little lighter, more saturated than Great Hall Grey.

Can I use Sand Grey instead of Great Hall Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Sand Grey is a little lighter, more saturated than Great Hall Grey.

Can I use Great Hall Grey instead of Sand Grey?

The same difference applies the other way round: Great Hall Grey 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.