Iridescent Copper (Coarse) vs Grunge Brown

How close are they?

ΔE 7.5, close: similar, with a visible difference side by side. Grunge Brown is more saturated than Iridescent Copper (Coarse). They are different kinds of paint: Golden Iridescent Copper (Coarse) is a pearl paint and Vallejo Grunge Brown is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.

Can I use Grunge Brown instead of Iridescent Copper (Coarse)?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Grunge Brown is more saturated than Iridescent Copper (Coarse). They are different kinds of paint.

Can I use Iridescent Copper (Coarse) instead of Grunge Brown?

The same difference applies the other way round: Iridescent Copper (Coarse) is 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.