Centurion Red vs Red RLM23

How close are they?

ΔE 8.9, close: similar, with a visible difference side by side. Red RLM23 is a little darker, more muted than Centurion Red.

Can I use Red RLM23 instead of Centurion Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Red RLM23 is a little darker, more muted than Centurion Red.

Can I use Centurion Red instead of Red RLM23?

The same difference applies the other way round: Centurion 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.