WWI German Mauve vs Necromancer Cloak

How close are they?

ΔE 17.0, loose: different enough that you should pick on purpose. Necromancer Cloak is noticeably darker, more muted, cooler than WWI German Mauve.

Can I use Necromancer Cloak instead of WWI German Mauve?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Necromancer Cloak is noticeably darker, more muted, cooler than WWI German Mauve.

Can I use WWI German Mauve instead of Necromancer Cloak?

The same difference applies the other way round: WWI German Mauve is noticeably lighter, more saturated, warmer.

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.