Poppy Red vs Slaughter Red

How close are they?

ΔE 19.4, loose: different enough that you should pick on purpose. Slaughter Red is noticeably darker, more muted than Poppy Red.

Can I use Slaughter Red instead of Poppy Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Slaughter Red is noticeably darker, more muted than Poppy Red.

Can I use Poppy Red instead of Slaughter Red?

The same difference applies the other way round: Poppy Red 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.