ΔE 23.7, loose: different enough that you should pick on purpose. N7 Neutral Gray is much more muted than Lucius Lilac.
Can I use N7 Neutral Gray instead of Lucius Lilac?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). N7 Neutral Gray is much more muted than Lucius Lilac.
Can I use Lucius Lilac instead of N7 Neutral Gray?
The same difference applies the other way round: Lucius Lilac is 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.