Typhon Ash vs Sandstone

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Sandstone is a little darker, more saturated than Typhon Ash.

Can I use Sandstone instead of Typhon Ash?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Sandstone is a little darker, more saturated than Typhon Ash.

Can I use Typhon Ash instead of Sandstone?

The same difference applies the other way round: Typhon Ash is a little lighter, 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.