ΔE 23.5, loose: different enough that you should pick on purpose. Ruby Red is a little lighter, more saturated, warmer than Carroburg Crimson. They are different kinds of paint: Citadel Carroburg Crimson is a wash/shade and Nocturna Models Ruby Red is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Ruby Red is a little lighter, more saturated, warmer than Carroburg Crimson. They are different kinds of paint.
The same difference applies the other way round: Carroburg Crimson is a little darker, more muted, 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.
See Carroburg Crimson on the colour wheel See Ruby Red on the colour wheel
All matches: Carroburg Crimson equivalents · Ruby Red equivalents