ΔE 26.8, loose: different enough that you should pick on purpose. Iridescent Gold (Fine) is a little lighter, much more saturated than Polished Silver. They are different kinds of paint: Army Painter Polished Silver is a metallic and Golden Iridescent Gold (Fine) is a pearl paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Iridescent Gold (Fine) is a little lighter, much more saturated than Polished Silver. They are different kinds of paint.
The same difference applies the other way round: Polished 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.
See Polished Silver on the colour wheel See Iridescent Gold (Fine) on the colour wheel
All matches: Polished Silver equivalents · Iridescent Gold (Fine) equivalents