ΔE 15.1, loose: different enough that you should pick on purpose. Jade Green is a little lighter, much more saturated than Kroak Green. They are different kinds of paint: Citadel Kroak Green is a wash/shade and Reaper Jade 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 15). Jade Green is a little lighter, much more saturated than Kroak Green. They are different kinds of paint.
The same difference applies the other way round: Kroak Green is a little darker, much more muted.
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 Kroak Green on the colour wheel See Jade Green on the colour wheel
All matches: Kroak Green equivalents · Jade Green equivalents