ΔE 17.4, loose: different enough that you should pick on purpose. Undergrowth Green is a little lighter, much more saturated, warmer than Orc Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Undergrowth Green is a little lighter, much more saturated, warmer than Orc Flesh.
The same difference applies the other way round: Orc Flesh is a little darker, much 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 Orc Flesh on the colour wheel See Undergrowth Green on the colour wheel
All matches: Orc Flesh equivalents · Undergrowth Green equivalents