Broadsword Silver vs Dark Silver

How close are they?

ΔE 6.0, close: similar, with a visible difference side by side. Dark Silver is a little lighter than Broadsword Silver.

Can I use Dark Silver instead of Broadsword Silver?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Dark Silver is a little lighter than Broadsword Silver.

Can I use Broadsword Silver instead of Dark Silver?

The same difference applies the other way round: Broadsword Silver is a little darker.

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.