ΔE 12.8, fair: the same colour family, but not a straight swap. Ink Violet is a little lighter, more muted than Purple Tone. They are different kinds of paint: Army Painter Purple Tone is a wash/shade and Vallejo Ink Violet 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). Ink Violet is a little lighter, more muted than Purple Tone. They are different kinds of paint.
The same difference applies the other way round: Purple Tone is a little darker, 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 Purple Tone on the colour wheel See Ink Violet on the colour wheel
All matches: Purple Tone equivalents · Ink Violet equivalents