Sparkling Amethyst vs Steel (Metallic)

How close are they?

ΔE 36.6, loose: different enough that you should pick on purpose. Steel (Metallic) is noticeably lighter, much more muted than Sparkling Amethyst.

Can I use Steel (Metallic) instead of Sparkling Amethyst?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 37). Steel (Metallic) is noticeably lighter, much more muted than Sparkling Amethyst.

Can I use Sparkling Amethyst instead of Steel (Metallic)?

The same difference applies the other way round: Sparkling Amethyst is noticeably darker, much more saturated.

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.