Molten Orange vs Intense Brown

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Intense Brown is a little darker, more muted than Molten Orange.

Can I use Intense Brown instead of Molten Orange?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Intense Brown is a little darker, more muted than Molten Orange.

Can I use Molten Orange instead of Intense Brown?

The same difference applies the other way round: Molten Orange 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.