Spectral Purple vs Deep Magenta

How close are they?

ΔE 21.2, loose: different enough that you should pick on purpose. Deep Magenta is noticeably darker, warmer than Spectral Purple.

Can I use Deep Magenta instead of Spectral Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Deep Magenta is noticeably darker, warmer than Spectral Purple.

Can I use Spectral Purple instead of Deep Magenta?

The same difference applies the other way round: Spectral Purple is noticeably lighter, 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.