ΔE 14.8, fair: the same colour family, but not a straight swap. Magos Purple is noticeably darker, more saturated than Matt Violet. They are different kinds of paint: AMMO by Mig Matt Violet is an ink, glaze or transparent paint and Citadel Magos Purple is a one-coat contrast-style 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 15). Magos Purple is noticeably darker, more saturated than Matt Violet. They are different kinds of paint.
The same difference applies the other way round: Matt Violet is noticeably lighter, more muted.
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 Violet on the colour wheel See Magos Purple on the colour wheel
All matches: Matt Violet equivalents · Magos Purple equivalents