Sanguine Highlight vs Magenta

How close are they?

ΔE 30.9, loose: different enough that you should pick on purpose. Magenta is noticeably darker, much more muted, cooler than Sanguine Highlight.

Can I use Magenta instead of Sanguine Highlight?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Magenta is noticeably darker, much more muted, cooler than Sanguine Highlight.

Can I use Sanguine Highlight instead of Magenta?

The same difference applies the other way round: Sanguine Highlight is noticeably lighter, much more saturated, 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.