ΔE 12.1, fair: the same colour family, but not a straight swap. Dk Mediterr. Blue is a little darker, more muted, cooler than Royal Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Dk Mediterr. Blue is a little darker, more muted, cooler than Royal Blue.
The same difference applies the other way round: Royal Blue is a little lighter, more saturated, warmer.
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 Royal Blue on the colour wheel See Dk Mediterr. Blue on the colour wheel
All matches: Royal Blue equivalents · Dk Mediterr. Blue equivalents