ΔE 11.3, fair: the same colour family, but not a straight swap. Phthalo Green is a little lighter, cooler than Sons of Horus Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Phthalo Green is a little lighter, cooler than Sons of Horus Green.
The same difference applies the other way round: Sons of Horus Green is a little darker, warmer.
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 Phthalo Green on the colour wheel
All matches: Sons of Horus Green equivalents · Phthalo Green equivalents