Death Korps Drab vs Gangrene

How close are they?

ΔE 16.4, loose: different enough that you should pick on purpose. Gangrene is noticeably darker, more saturated than Death Korps Drab.

Can I use Gangrene instead of Death Korps Drab?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Gangrene is noticeably darker, more saturated than Death Korps Drab.

Can I use Death Korps Drab instead of Gangrene?

The same difference applies the other way round: Death Korps Drab is noticeably 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.