ΔE 12.0, fair: the same colour family, but not a straight swap. Park Green Flat is a little darker, more muted than Majestic Fortress.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Park Green Flat is a little darker, more muted than Majestic Fortress.
The same difference applies the other way round: Majestic Fortress is a little 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 Majestic Fortress on the colour wheel See Park Green Flat on the colour wheel
All matches: Majestic Fortress equivalents · Park Green Flat equivalents