Guilliman Flesh vs Phoenix Egg

How close are they?

ΔE 22.9, loose: different enough that you should pick on purpose. Phoenix Egg is noticeably lighter, more muted, cooler than Guilliman Flesh.

Can I use Phoenix Egg instead of Guilliman Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Phoenix Egg is noticeably lighter, more muted, cooler than Guilliman Flesh.

Can I use Guilliman Flesh instead of Phoenix Egg?

The same difference applies the other way round: Guilliman Flesh is noticeably 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.