Screamer Pink vs Dusky Grape

How close are they?

ΔE 20.6, loose: different enough that you should pick on purpose. Dusky Grape is a little darker, more muted, cooler than Screamer Pink.

Can I use Dusky Grape instead of Screamer Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Dusky Grape is a little darker, more muted, cooler than Screamer Pink.

Can I use Screamer Pink instead of Dusky Grape?

The same difference applies the other way round: Screamer Pink is a little lighter, 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.