Leviathan Purple vs Gloomy Violet

How close are they?

ΔE 23.3, loose: different enough that you should pick on purpose. Gloomy Violet is a little darker, much more muted than Leviathan Purple.

Can I use Gloomy Violet instead of Leviathan Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Gloomy Violet is a little darker, much more muted than Leviathan Purple.

Can I use Leviathan Purple instead of Gloomy Violet?

The same difference applies the other way round: Leviathan Purple is a little lighter, much 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.