Leviathan Purple vs Indigo Blue

How close are they?

ΔE 31.8, loose: different enough that you should pick on purpose. Indigo Blue is much more muted, cooler than Leviathan Purple.

Can I use Indigo Blue instead of Leviathan Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Indigo Blue is much more muted, cooler than Leviathan Purple.

Can I use Leviathan Purple instead of Indigo Blue?

The same difference applies the other way round: Leviathan Purple is 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.