ΔE 14.1, fair: the same colour family, but not a straight swap. Flat Blue is noticeably lighter, more muted than Lapislazuli.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Flat Blue is noticeably lighter, more muted than Lapislazuli.
The same difference applies the other way round: Lapislazuli is noticeably 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 Lapislazuli on the colour wheel See Flat Blue on the colour wheel
All matches: Lapislazuli equivalents · Flat Blue equivalents