RAF Sky / FS 34424 vs Terminatus Stone

How close are they?

ΔE 7.8, close: similar, with a visible difference side by side. Terminatus Stone is a little lighter, more saturated, warmer than RAF Sky / FS 34424.

Can I use Terminatus Stone instead of RAF Sky / FS 34424?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Terminatus Stone is a little lighter, more saturated, warmer than RAF Sky / FS 34424.

Can I use RAF Sky / FS 34424 instead of Terminatus Stone?

The same difference applies the other way round: RAF Sky / FS 34424 is a little darker, more muted, 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.