ΔE 12.9, fair: the same colour family, but not a straight swap. Swamp Brown is more muted, cooler than Skrag Brown. They are different kinds of paint: Citadel Skrag Brown is an opaque base/layer paint and Green Stuff World Swamp Brown is an ink, glaze or transparent 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 13). Swamp Brown is more muted, cooler than Skrag Brown. They are different kinds of paint.
The same difference applies the other way round: Skrag Brown is 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 Skrag Brown on the colour wheel See Swamp Brown on the colour wheel
All matches: Skrag Brown equivalents · Swamp Brown equivalents