Chaotic Red vs Chestnut Brown

How close are they?

ΔE 7.3, close: similar, with a visible difference side by side. Chestnut Brown is more saturated, warmer than Chaotic Red.

Can I use Chestnut Brown instead of Chaotic Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Chestnut Brown is more saturated, warmer than Chaotic Red.

Can I use Chaotic Red instead of Chestnut Brown?

The same difference applies the other way round: Chaotic Red is 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.