Baron Blue vs Lucius Lilac

How close are they?

ΔE 15.5, loose: different enough that you should pick on purpose. Lucius Lilac is a little lighter, more muted, warmer than Baron Blue.

Can I use Lucius Lilac instead of Baron Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Lucius Lilac is a little lighter, more muted, warmer than Baron Blue.

Can I use Baron Blue instead of Lucius Lilac?

The same difference applies the other way round: Baron Blue is a little darker, more saturated, cooler.

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.