ΔE 12.3, fair: the same colour family, but not a straight swap. Oxford Blue is a little lighter, warmer than Ritterlich Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Oxford Blue is a little lighter, warmer than Ritterlich Blue.
The same difference applies the other way round: Ritterlich Blue is a little darker, 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 Ritterlich Blue on the colour wheel See Oxford Blue on the colour wheel
All matches: Ritterlich Blue equivalents · Oxford Blue equivalents