Tainted Garden vs Battlefield Brown

How close are they?

ΔE 16.7, loose: different enough that you should pick on purpose. Battlefield Brown is noticeably darker, more muted than Tainted Garden.

Can I use Battlefield Brown instead of Tainted Garden?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Battlefield Brown is noticeably darker, more muted than Tainted Garden.

Can I use Tainted Garden instead of Battlefield Brown?

The same difference applies the other way round: Tainted Garden is noticeably 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.