ΔE 21.1, loose: different enough that you should pick on purpose. Gnarls Green is a little darker, more saturated, warmer than Sons of Horus Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Gnarls Green is a little darker, more saturated, warmer than Sons of Horus Green.
The same difference applies the other way round: Sons of Horus Green is a little lighter, 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 Sons of Horus Green on the colour wheel See Gnarls Green on the colour wheel
All matches: Sons of Horus Green equivalents · Gnarls Green equivalents