Apocalypse Sky vs Red RLM23

How close are they?

ΔE 11.7, fair: the same colour family, but not a straight swap. Red RLM23 is noticeably darker, more saturated than Apocalypse Sky.

Can I use Red RLM23 instead of Apocalypse Sky?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Red RLM23 is noticeably darker, more saturated than Apocalypse Sky.

Can I use Apocalypse Sky instead of Red RLM23?

The same difference applies the other way round: Apocalypse Sky is noticeably lighter, more muted.

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.