Ember Orange vs Leather Brown

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Leather Brown is more muted, cooler than Ember Orange.

Can I use Leather Brown instead of Ember Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Leather Brown is more muted, cooler than Ember Orange.

Can I use Ember Orange instead of Leather Brown?

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