Broadsword Silver vs Storm Surge Green

How close are they?

ΔE 26.9, loose: different enough that you should pick on purpose. Storm Surge Green is a little lighter, much more saturated than Broadsword Silver.

Can I use Storm Surge Green instead of Broadsword Silver?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Storm Surge Green is a little lighter, much more saturated than Broadsword Silver.

Can I use Broadsword Silver instead of Storm Surge Green?

The same difference applies the other way round: Broadsword Silver 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.