ΔE 14.6, fair: the same colour family, but not a straight swap. Medium Blue is noticeably darker, more muted than Shieldwall Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Medium Blue is noticeably darker, more muted than Shieldwall Blue.
The same difference applies the other way round: Shieldwall Blue is noticeably lighter, 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 Shieldwall Blue on the colour wheel See Medium Blue on the colour wheel
All matches: Shieldwall Blue equivalents · Medium Blue equivalents