ΔE 16.2, loose: different enough that you should pick on purpose. Iridescent Bright Gold (Fine) is noticeably lighter, more saturated, warmer than Skullcrusher Brass. They are different kinds of paint: Citadel Skullcrusher Brass is a metallic and Golden Iridescent Bright 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 16). Iridescent Bright Gold (Fine) is noticeably lighter, more saturated, warmer than Skullcrusher Brass. They are different kinds of paint.
The same difference applies the other way round: Skullcrusher Brass is noticeably darker, more muted, cooler.
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 Skullcrusher Brass on the colour wheel See Iridescent Bright Gold (Fine) on the colour wheel
All matches: Skullcrusher Brass equivalents · Iridescent Bright Gold (Fine) equivalents