ΔE 16.4, loose: different enough that you should pick on purpose. Light Phthalo Green is noticeably lighter, more saturated, warmer than Toxic Mist.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Light Phthalo Green is noticeably lighter, more saturated, warmer than Toxic Mist.
The same difference applies the other way round: Toxic Mist is noticeably darker, 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 Toxic Mist on the colour wheel See Light Phthalo Green on the colour wheel
All matches: Toxic Mist equivalents · Light Phthalo Green equivalents