ΔE 11.4, fair: the same colour family, but not a straight swap. Signal Blue is a little lighter, more saturated than NATO Black.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Signal Blue is a little lighter, more saturated than NATO Black.
The same difference applies the other way round: NATO Black is a little darker, more muted.
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 NATO Black on the colour wheel See Signal Blue on the colour wheel
All matches: NATO Black equivalents · Signal Blue equivalents