ΔE 14.5, fair: the same colour family, but not a straight swap. Olive Green is much more muted, warmer than Gnarls Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Olive Green is much more muted, warmer than Gnarls Green.
The same difference applies the other way round: Gnarls Green is much 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.
See Gnarls Green on the colour wheel See Olive Green on the colour wheel
All matches: Gnarls Green equivalents · Olive Green equivalents