ΔE 9.6, close: similar, with a visible difference side by side. Fluorescent Violet is more saturated than Xereus Purple. They are different kinds of paint: Citadel Xereus Purple is an opaque base/layer paint and Vallejo Fluorescent Violet is a fluorescent or effect 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 10). Fluorescent Violet is more saturated than Xereus Purple. They are different kinds of paint.
The same difference applies the other way round: Xereus Purple is 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 Xereus Purple on the colour wheel See Fluorescent Violet on the colour wheel
All matches: Xereus Purple equivalents · Fluorescent Violet equivalents