ΔE 15.8, loose: different enough that you should pick on purpose. Goblin Green is noticeably lighter, more saturated, warmer than Undergrowth Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Goblin Green is noticeably lighter, more saturated, warmer than Undergrowth Green.
The same difference applies the other way round: Undergrowth Green is noticeably darker, more muted, 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.
See Undergrowth Green on the colour wheel See Goblin Green on the colour wheel
All matches: Undergrowth Green equivalents · Goblin Green equivalents