Dark Red vs Beret Maroon

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Beret Maroon is a little darker, more muted than Dark Red.

Can I use Beret Maroon instead of Dark Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Beret Maroon is a little darker, more muted than Dark Red.

Can I use Dark Red instead of Beret Maroon?

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

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.