ΔE 10.6, fair: the same colour family, but not a straight swap. Insignia White (US Navy) is a little lighter than Ulthuan Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Insignia White (US Navy) is a little lighter than Ulthuan Grey.
The same difference applies the other way round: Ulthuan Grey is a little darker.
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 Ulthuan Grey on the colour wheel See Insignia White (US Navy) on the colour wheel
All matches: Ulthuan Grey equivalents · Insignia White (US Navy) equivalents