ΔE 13.5, fair: the same colour family, but not a straight swap. German Orange is a little darker, much more muted than Ruby.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). German Orange is a little darker, much more muted than Ruby.
The same difference applies the other way round: Ruby is a little lighter, much 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.
See Ruby on the colour wheel See German Orange on the colour wheel
All matches: Ruby equivalents · German Orange equivalents