Typhon Ash vs German Dark Yellow

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. German Dark Yellow is a little darker, more saturated than Typhon Ash.

Can I use German Dark Yellow instead of Typhon Ash?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). German Dark Yellow is a little darker, more saturated than Typhon Ash.

Can I use Typhon Ash instead of German Dark Yellow?

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.