ΔE 17.2, loose: different enough that you should pick on purpose. Phthalo Green (Yellow Shade) is a little lighter, much more saturated than Warboss Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Phthalo Green (Yellow Shade) is a little lighter, much more saturated than Warboss Green.
The same difference applies the other way round: Warboss Green is a little 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 Warboss Green on the colour wheel See Phthalo Green (Yellow Shade) on the colour wheel
All matches: Warboss Green equivalents · Phthalo Green (Yellow Shade) equivalents