ΔE 15.5, loose: different enough that you should pick on purpose. Stone Grey is noticeably lighter, warmer than Mage Hunter Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Stone Grey is noticeably lighter, warmer than Mage Hunter Green.
The same difference applies the other way round: Mage Hunter Green 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 Mage Hunter Green on the colour wheel See Stone Grey on the colour wheel
All matches: Mage Hunter Green equivalents · Stone Grey equivalents