Arcane Purple vs Gloomy Violet

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Gloomy Violet is a little lighter, more muted, cooler than Arcane Purple.

Can I use Gloomy Violet instead of Arcane Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Gloomy Violet is a little lighter, more muted, cooler than Arcane Purple.

Can I use Arcane Purple instead of Gloomy Violet?

The same difference applies the other way round: Arcane Purple is a little darker, 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.