ΔE 19.1, loose: different enough that you should pick on purpose. Emerald is noticeably darker, much more muted, cooler than Bright Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Emerald is noticeably darker, much more muted, cooler than Bright Green.
The same difference applies the other way round: Bright Green is noticeably lighter, much 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 Bright Green on the colour wheel See Emerald on the colour wheel
All matches: Bright Green equivalents · Emerald equivalents