ΔE 7.4, close: similar, with a visible difference side by side. Transparent Purple is a little darker, more muted than Leviathan Purple. They are different kinds of paint: Citadel Leviathan Purple 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.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Transparent Purple is a little darker, more muted than Leviathan Purple. They are different kinds of paint.
The same difference applies the other way round: Leviathan Purple is a little lighter, 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 Leviathan Purple on the colour wheel See Transparent Purple on the colour wheel
All matches: Leviathan Purple equivalents · Transparent Purple equivalents