ΔE 25.6, loose: different enough that you should pick on purpose. Eldritch is noticeably darker, much more muted, cooler than Ghoul Green. They are different kinds of paint: Army Painter Ghoul Green is a one-coat contrast-style paint and Formula P3 Eldritch 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 26). Eldritch is noticeably darker, much more muted, cooler than Ghoul Green. They are different kinds of paint.
The same difference applies the other way round: Ghoul Green is noticeably lighter, much more saturated, warmer.
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 Eldritch on the colour wheel
All matches: Ghoul Green equivalents · Eldritch equivalents