Lucius Lilac vs Neo Pink

How close are they?

ΔE 18.7, loose: different enough that you should pick on purpose. Neo Pink is a little lighter, warmer than Lucius Lilac.

Can I use Neo Pink instead of Lucius Lilac?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Neo Pink is a little lighter, warmer than Lucius Lilac.

Can I use Lucius Lilac instead of Neo Pink?

The same difference applies the other way round: Lucius Lilac is a little darker, 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.