ΔE 22.3, loose: different enough that you should pick on purpose. Light Phthalo Green is noticeably lighter, warmer than Neptune Glow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Light Phthalo Green is noticeably lighter, warmer than Neptune Glow.
The same difference applies the other way round: Neptune Glow is noticeably darker, 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 Neptune Glow on the colour wheel See Light Phthalo Green on the colour wheel
All matches: Neptune Glow equivalents · Light Phthalo Green equivalents