Grey Blue vs Lustful Purple

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Lustful Purple is a little lighter, more saturated, warmer than Grey Blue.

Can I use Lustful Purple instead of Grey Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Lustful Purple is a little lighter, more saturated, warmer than Grey Blue.

Can I use Grey Blue instead of Lustful Purple?

The same difference applies the other way round: Grey Blue is a little darker, more muted, 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.