Stormhost Silver vs Silver Sun

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Silver Sun is a little lighter than Stormhost Silver.

Can I use Silver Sun instead of Stormhost Silver?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Silver Sun is a little lighter than Stormhost Silver.

Can I use Stormhost Silver instead of Silver Sun?

The same difference applies the other way round: Stormhost 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.