ΔE 17.5, loose: different enough that you should pick on purpose. Putrid Green is noticeably darker, cooler than Pestilent Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Putrid Green is noticeably darker, cooler than Pestilent Flesh.
The same difference applies the other way round: Pestilent Flesh is noticeably lighter, 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 Pestilent Flesh on the colour wheel See Putrid Green on the colour wheel
All matches: Pestilent Flesh equivalents · Putrid Green equivalents