Terminatus Stone vs Deck Grey

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Deck Grey is warmer than Terminatus Stone.

Can I use Deck Grey instead of Terminatus Stone?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Deck Grey is warmer than Terminatus Stone.

Can I use Terminatus Stone instead of Deck Grey?

The same difference applies the other way round: Terminatus Stone is 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.