Murderous Magenta vs Sunset Red

How close are they?

ΔE 15.9, loose: different enough that you should pick on purpose. Sunset Red is a little lighter, warmer than Murderous Magenta.

Can I use Sunset Red instead of Murderous Magenta?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Sunset Red is a little lighter, warmer than Murderous Magenta.

Can I use Murderous Magenta instead of Sunset Red?

The same difference applies the other way round: Murderous Magenta is a little darker, 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.