Pink Flesh vs Fulgrim Pink

How close are they?

ΔE 23.4, loose: different enough that you should pick on purpose. Fulgrim Pink is noticeably lighter, cooler than Pink Flesh.

Can I use Fulgrim Pink instead of Pink Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Fulgrim Pink is noticeably lighter, cooler than Pink Flesh.

Can I use Pink Flesh instead of Fulgrim Pink?

The same difference applies the other way round: Pink Flesh is noticeably darker, 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.