Fulgrim Pink vs Runic Purple

How close are they?

ΔE 26.1, loose: different enough that you should pick on purpose. Runic Purple is noticeably darker, more muted, cooler than Fulgrim Pink.

Can I use Runic Purple instead of Fulgrim Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Runic Purple is noticeably darker, more muted, cooler than Fulgrim Pink.

Can I use Fulgrim Pink instead of Runic Purple?

The same difference applies the other way round: Fulgrim Pink is noticeably lighter, 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.