ΔE 11.5, fair: the same colour family, but not a straight swap. Papyrus is cooler than Agrellan Earth. They are different kinds of paint: Citadel Agrellan Earth is a technical paint or medium and Green Stuff World Papyrus is a one-coat contrast-style 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 12). Papyrus is cooler than Agrellan Earth. They are different kinds of paint.
The same difference applies the other way round: Agrellan Earth is 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 Papyrus on the colour wheel
All matches: Agrellan Earth equivalents · Papyrus equivalents