Hastur Purple vs Magenta

How close are they?

ΔE 15.0, loose: different enough that you should pick on purpose. Magenta is a little lighter, more saturated, cooler than Hastur Purple.

Can I use Magenta instead of Hastur Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Magenta is a little lighter, more saturated, cooler than Hastur Purple.

Can I use Hastur Purple instead of Magenta?

The same difference applies the other way round: Hastur Purple is a little darker, 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.