Genestealer Purple vs Witching Hour Blue

How close are they?

ΔE 35.6, loose: different enough that you should pick on purpose. Witching Hour Blue is a little lighter, much more muted, cooler than Genestealer Purple.

Can I use Witching Hour Blue instead of Genestealer Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 36). Witching Hour Blue is a little lighter, much more muted, cooler than Genestealer Purple.

Can I use Genestealer Purple instead of Witching Hour Blue?

The same difference applies the other way round: Genestealer Purple is a little darker, much more saturated, warmer.

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.