ΔE 23.4, loose: different enough that you should pick on purpose. Sick Green is a little darker, more muted, cooler than Olive Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sick Green is a little darker, more muted, cooler than Olive Green.
The same difference applies the other way round: Olive Green is a little lighter, 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.
See Olive Green on the colour wheel See Sick Green on the colour wheel
All matches: Olive Green equivalents · Sick Green equivalents