Skyrat vs Gunmetal Blue

How close are they?

ΔE 18.6, loose: different enough that you should pick on purpose. Gunmetal Blue is noticeably darker, more muted, warmer than Skyrat.

Can I use Gunmetal Blue instead of Skyrat?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Gunmetal Blue is noticeably darker, more muted, warmer than Skyrat.

Can I use Skyrat instead of Gunmetal Blue?

The same difference applies the other way round: Skyrat is noticeably lighter, more saturated, 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.