ΔE 17.1, loose: different enough that you should pick on purpose. Bright Green is much more muted, warmer than Orc Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Bright Green is much more muted, warmer than Orc Green.
The same difference applies the other way round: Orc Green is much more saturated, cooler.
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 Orc Green on the colour wheel See Bright Green on the colour wheel
All matches: Orc Green equivalents · Bright Green equivalents