Plate Armour vs Amethyst Purple

How close are they?

ΔE 40.2, loose: different enough that you should pick on purpose. Amethyst Purple is a little darker, much more saturated than Plate Armour.

Can I use Amethyst Purple instead of Plate Armour?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Amethyst Purple is a little darker, much more saturated than Plate Armour.

Can I use Plate Armour instead of Amethyst Purple?

The same difference applies the other way round: Plate Armour is a little lighter, 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.