Red Brown vs US Earth Red

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. US Earth Red is a little lighter, more muted, warmer than Red Brown.

Can I use US Earth Red instead of Red Brown?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). US Earth Red is a little lighter, more muted, warmer than Red Brown.

Can I use Red Brown instead of US Earth Red?

The same difference applies the other way round: Red Brown is a little darker, more saturated, 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.