ΔE 30.6, loose: different enough that you should pick on purpose. Misted Yellow is noticeably darker, much more saturated, cooler than Guilliman Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Misted Yellow is noticeably darker, much more saturated, cooler than Guilliman Flesh.
The same difference applies the other way round: Guilliman Flesh is noticeably lighter, much more muted, 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.
See Guilliman Flesh on the colour wheel See Misted Yellow on the colour wheel
All matches: Guilliman Flesh equivalents · Misted Yellow equivalents