ΔE 9.2, close: similar, with a visible difference side by side. Brown is a little darker, more saturated than Knight-Questor Flesh. They are different kinds of paint: Citadel Knight-Questor Flesh is an opaque base/layer paint and Green Stuff World Brown is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Brown is a little darker, more saturated than Knight-Questor Flesh. They are different kinds of paint.
The same difference applies the other way round: Knight-Questor Flesh is a little lighter, 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 Knight-Questor Flesh on the colour wheel See Brown on the colour wheel
All matches: Knight-Questor Flesh equivalents · Brown equivalents