Murderous Magenta vs Worn Red

How close are they?

ΔE 28.3, loose: different enough that you should pick on purpose. Worn Red is noticeably lighter, more saturated, warmer than Murderous Magenta.

Can I use Worn Red instead of Murderous Magenta?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Worn Red is noticeably lighter, more saturated, warmer than Murderous Magenta.

Can I use Murderous Magenta instead of Worn Red?

The same difference applies the other way round: Murderous Magenta is noticeably darker, more muted, 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.