Screamer Pink vs Flat Brown

How close are they?

ΔE 19.2, loose: different enough that you should pick on purpose. Flat Brown is much more muted, warmer than Screamer Pink.

Can I use Flat Brown instead of Screamer Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Flat Brown is much more muted, warmer than Screamer Pink.

Can I use Screamer Pink instead of Flat Brown?

The same difference applies the other way round: Screamer Pink is much more saturated, cooler.

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.