Transparent Brown vs Mahogany Ink

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Mahogany Ink is more muted, cooler than Transparent Brown.

Can I use Mahogany Ink instead of Transparent Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Mahogany Ink is more muted, cooler than Transparent Brown.

Can I use Transparent Brown instead of Mahogany Ink?

The same difference applies the other way round: Transparent Brown 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.