ΔE 4.5, very close: most people won’t see a difference side by side. Siena is more muted than Knight-Questor Flesh. They are different kinds of paint: Citadel Knight-Questor Flesh is an opaque base/layer paint and Green Stuff World Siena is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 4). Siena is more muted than Knight-Questor Flesh. They are different kinds of paint.
The same difference applies the other way round: Knight-Questor Flesh is more saturated.
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 Siena on the colour wheel
All matches: Knight-Questor Flesh equivalents · Siena equivalents