Cardinal Purple vs Khorne Red

How close are they?

ΔE 15.5, loose: different enough that you should pick on purpose. Khorne Red is much more saturated, cooler than Cardinal Purple.

Can I use Khorne Red instead of Cardinal Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Khorne Red is much more saturated, cooler than Cardinal Purple.

Can I use Cardinal Purple instead of Khorne Red?

The same difference applies the other way round: Cardinal Purple is much more muted, 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.