Tinmetal Grey vs Gunmetal (Metal.)

How close are they?

ΔE 17.7, loose: different enough that you should pick on purpose. Gunmetal (Metal.) is noticeably lighter, more muted than Tinmetal Grey.

Can I use Gunmetal (Metal.) instead of Tinmetal Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Gunmetal (Metal.) is noticeably lighter, more muted than Tinmetal Grey.

Can I use Tinmetal Grey instead of Gunmetal (Metal.)?

The same difference applies the other way round: Tinmetal Grey is noticeably darker, 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.