ΔE 18.2, loose: different enough that you should pick on purpose. Phthalo Green (Yellow Shade) is noticeably lighter, much more saturated than Savage Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Phthalo Green (Yellow Shade) is noticeably lighter, much more saturated than Savage Green.
The same difference applies the other way round: Savage Green is noticeably darker, much more muted.
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 Savage Green on the colour wheel See Phthalo Green (Yellow Shade) on the colour wheel
All matches: Savage Green equivalents · Phthalo Green (Yellow Shade) equivalents