Dark Emerald vs Necro Gold

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Necro Gold is noticeably lighter, more muted, warmer than Dark Emerald.

Can I use Necro Gold instead of Dark Emerald?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Necro Gold is noticeably lighter, more muted, warmer than Dark Emerald.

Can I use Dark Emerald instead of Necro Gold?

The same difference applies the other way round: Dark Emerald is noticeably darker, more saturated, 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.