Murderous Magenta vs Warlord Purple

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Warlord Purple is a little lighter, more muted than Murderous Magenta.

Can I use Warlord Purple instead of Murderous Magenta?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Warlord Purple is a little lighter, more muted than Murderous Magenta.

Can I use Murderous Magenta instead of Warlord Purple?

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