ΔE 17.8, loose: different enough that you should pick on purpose. Feral Green is noticeably darker, more muted, warmer than Deep Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Feral Green is noticeably darker, more muted, warmer than Deep Green.
The same difference applies the other way round: Deep Green is noticeably lighter, more saturated, 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 Deep Green on the colour wheel See Feral Green on the colour wheel
All matches: Deep Green equivalents · Feral Green equivalents