ΔE 13.7, fair: the same colour family, but not a straight swap. Imp Yellow is a little lighter, much more muted than Matt Hazelnut. They are different kinds of paint: AMMO by Mig Matt Hazelnut is an ink, glaze or transparent paint and Army Painter Imp Yellow is an opaque base/layer 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 14). Imp Yellow is a little lighter, much more muted than Matt Hazelnut. They are different kinds of paint.
The same difference applies the other way round: Matt Hazelnut is a little darker, much 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 Matt Hazelnut on the colour wheel See Imp Yellow on the colour wheel
All matches: Matt Hazelnut equivalents · Imp Yellow equivalents