ΔE 6.1, close: similar, with a visible difference side by side. Iridescent Copper (Fine) is a little lighter, warmer than Knight-Questor Flesh. They are different kinds of paint: Citadel Knight-Questor Flesh is an opaque base/layer paint and Golden Iridescent Copper (Fine) is a pearl 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 6). Iridescent Copper (Fine) is a little lighter, warmer than Knight-Questor Flesh. They are different kinds of paint.
The same difference applies the other way round: Knight-Questor Flesh is a little darker, cooler.
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 Iridescent Copper (Fine) on the colour wheel
All matches: Knight-Questor Flesh equivalents · Iridescent Copper (Fine) equivalents