ΔE 8.2, close: similar, with a visible difference side by side. Typhon Ash is a little lighter than Dark Ghost Gray.
Can I use Typhon Ash instead of Dark Ghost Gray?
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Typhon Ash is a little lighter than Dark Ghost Gray.
Can I use Dark Ghost Gray instead of Typhon Ash?
The same difference applies the other way round: Dark Ghost Gray 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.