Necron Compound vs Polished Silver

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Polished Silver is a little darker than Necron Compound.

Can I use Polished Silver instead of Necron Compound?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Polished Silver is a little darker than Necron Compound.

Can I use Necron Compound instead of Polished Silver?

The same difference applies the other way round: Necron Compound is a little lighter.

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.