Slaanesh Grey vs Lustful Purple

How close are they?

ΔE 18.3, loose: different enough that you should pick on purpose. Lustful Purple is noticeably lighter, much more saturated than Slaanesh Grey.

Can I use Lustful Purple instead of Slaanesh Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Lustful Purple is noticeably lighter, much more saturated than Slaanesh Grey.

Can I use Slaanesh Grey instead of Lustful Purple?

The same difference applies the other way round: Slaanesh Grey is noticeably darker, much more muted.

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.