Familiar Pink vs Glorious Magenta

How close are they?

ΔE 40.8, loose: different enough that you should pick on purpose. Glorious Magenta is noticeably darker, much more muted, warmer than Familiar Pink.

Can I use Glorious Magenta instead of Familiar Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 41). Glorious Magenta is noticeably darker, much more muted, warmer than Familiar Pink.

Can I use Familiar Pink instead of Glorious Magenta?

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