ΔE 10.3, fair: the same colour family, but not a straight swap. Graphite Grey is a little lighter, more muted than Tyrian Navy.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Graphite Grey is a little lighter, more muted than Tyrian Navy.
The same difference applies the other way round: Tyrian Navy is a little darker, 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 Tyrian Navy on the colour wheel See Graphite Grey on the colour wheel
All matches: Tyrian Navy equivalents · Graphite Grey equivalents