Agent Orange vs Grunge Brown

How close are they?

ΔE 19.7, loose: different enough that you should pick on purpose. Grunge Brown is noticeably darker, more muted than Agent Orange.

Can I use Grunge Brown instead of Agent Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Grunge Brown is noticeably darker, more muted than Agent Orange.

Can I use Agent Orange instead of Grunge Brown?

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