ΔE 15.9, loose: different enough that you should pick on purpose. Leaf Green is noticeably darker, more muted than Ghoul Green. They are different kinds of paint: Army Painter Ghoul Green is a one-coat contrast-style paint and Reaper Leaf Green is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Leaf Green is noticeably darker, more muted than Ghoul Green. They are different kinds of paint.
The same difference applies the other way round: Ghoul Green is noticeably lighter, more saturated.
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 Ghoul Green on the colour wheel See Leaf Green on the colour wheel
All matches: Ghoul Green equivalents · Leaf Green equivalents