Flat Red vs Red RLM23

How close are they?

ΔE 13.0, fair: the same colour family, but not a straight swap. Red RLM23 is a little darker, more muted than Flat Red.

Can I use Red RLM23 instead of Flat Red?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Red RLM23 is a little darker, more muted than Flat Red.

Can I use Flat Red instead of Red RLM23?

The same difference applies the other way round: Flat 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.