Golden Shine vs Dark Gunmetal

How close are they?

ΔE 51.8, loose: different enough that you should pick on purpose. Dark Gunmetal is noticeably lighter, much more muted than Golden Shine.

Can I use Dark Gunmetal instead of Golden Shine?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 52). Dark Gunmetal is noticeably lighter, much more muted than Golden Shine.

Can I use Golden Shine instead of Dark Gunmetal?

The same difference applies the other way round: Golden Shine 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.