Primary Magenta vs Pink

How close are they?

ΔE 20.5, loose: different enough that you should pick on purpose. Pink is a little lighter, more muted, cooler than Primary Magenta.

Can I use Pink instead of Primary Magenta?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Pink is a little lighter, more muted, cooler than Primary Magenta.

Can I use Primary Magenta instead of Pink?

The same difference applies the other way round: Primary Magenta is a little darker, 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.