Majestic Fortress vs Green Oxide

How close are they?

ΔE 9.0, close: similar, with a visible difference side by side. Green Oxide is more muted, cooler than Majestic Fortress.

Can I use Green Oxide instead of Majestic Fortress?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Green Oxide is more muted, cooler than Majestic Fortress.

Can I use Majestic Fortress instead of Green Oxide?

The same difference applies the other way round: Majestic Fortress is more saturated, warmer.

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.