ΔE 10.9, fair: the same colour family, but not a straight swap. Dark Beige is a little lighter, more muted, cooler than Agrellan Earth. They are different kinds of paint: Citadel Agrellan Earth is a technical paint or medium and Green Stuff World Dark Beige is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Dark Beige is a little lighter, more muted, cooler than Agrellan Earth. They are different kinds of paint.
The same difference applies the other way round: Agrellan Earth is a little darker, 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 Agrellan Earth on the colour wheel See Dark Beige on the colour wheel
All matches: Agrellan Earth equivalents · Dark Beige equivalents