ΔE 19.0, loose: different enough that you should pick on purpose. Niblet Green is noticeably darker, cooler than Pacific Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Niblet Green is noticeably darker, cooler than Pacific Green.
The same difference applies the other way round: Pacific Green 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 Pacific Green on the colour wheel See Niblet Green on the colour wheel
All matches: Pacific Green equivalents · Niblet Green equivalents