ΔE 20.6, loose: different enough that you should pick on purpose. Park Green Flat is noticeably darker, much more muted than Bright Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Park Green Flat is noticeably darker, much more muted than Bright Green.
The same difference applies the other way round: Bright Green is noticeably lighter, much more saturated.
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 Bright Green on the colour wheel See Park Green Flat on the colour wheel
All matches: Bright Green equivalents · Park Green Flat equivalents