ΔE 9.2, close: similar, with a visible difference side by side. Nickel Azo Yellow is a little lighter than Fiendish Yellow. They are different kinds of paint: Army Painter Fiendish Yellow is an opaque base/layer paint and Golden Nickel Azo Yellow 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). Nickel Azo Yellow is a little lighter than Fiendish Yellow. They are different kinds of paint.
The same difference applies the other way round: Fiendish Yellow is a little darker.
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 Fiendish Yellow on the colour wheel See Nickel Azo Yellow on the colour wheel
All matches: Fiendish Yellow equivalents · Nickel Azo Yellow equivalents