Terracotta Pie vs Grunge Brown

How close are they?

ΔE 17.2, loose: different enough that you should pick on purpose. Grunge Brown is noticeably darker, more saturated than Terracotta Pie.

Can I use Grunge Brown instead of Terracotta Pie?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Grunge Brown is noticeably darker, more saturated than Terracotta Pie.

Can I use Terracotta Pie instead of Grunge Brown?

The same difference applies the other way round: Terracotta Pie is noticeably lighter, more muted.

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.