Permanent Violet Dark vs Warlord Purple

How close are they?

ΔE 32.3, loose: different enough that you should pick on purpose. Warlord Purple is noticeably lighter, warmer than Permanent Violet Dark.

Can I use Warlord Purple instead of Permanent Violet Dark?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Warlord Purple is noticeably lighter, warmer than Permanent Violet Dark.

Can I use Permanent Violet Dark instead of Warlord Purple?

The same difference applies the other way round: Permanent Violet Dark is noticeably 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.