ΔE 12.7, fair: the same colour family, but not a straight swap. Medium Magenta is cooler than Impish Rouge. They are different kinds of paint: Army Painter Impish Rouge is an opaque base/layer paint and Golden Medium Magenta is an ink, glaze or transparent 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 13). Medium Magenta is cooler than Impish Rouge. They are different kinds of paint.
The same difference applies the other way round: Impish Rouge is warmer.
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 Impish Rouge on the colour wheel See Medium Magenta on the colour wheel
All matches: Impish Rouge equivalents · Medium Magenta equivalents