Weapon Bronze vs Nebula Copper

How close are they?

ΔE 26.5, loose: different enough that you should pick on purpose. Nebula Copper is a little lighter, much more saturated than Weapon Bronze.

Can I use Nebula Copper instead of Weapon Bronze?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Nebula Copper is a little lighter, much more saturated than Weapon Bronze.

Can I use Weapon Bronze instead of Nebula Copper?

The same difference applies the other way round: Weapon Bronze is a little darker, 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.