ΔE 13.9, fair: the same colour family, but not a straight swap. Transparent Purple is a little darker, more muted, warmer than Beowulf Blue. They are different kinds of paint: Army Painter Beowulf Blue is a one-coat contrast-style paint and Green Stuff World Transparent Purple 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 14). Transparent Purple is a little darker, more muted, warmer than Beowulf Blue. They are different kinds of paint.
The same difference applies the other way round: Beowulf Blue is a little lighter, more saturated, cooler.
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 Beowulf Blue on the colour wheel See Transparent Purple on the colour wheel
All matches: Beowulf Blue equivalents · Transparent Purple equivalents