ΔE 21.2, loose: different enough that you should pick on purpose. Bright Green is a little darker, much more saturated, warmer than Viridian Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Bright Green is a little darker, much more saturated, warmer than Viridian Green.
The same difference applies the other way round: Viridian Green is a little lighter, much more muted, 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 Viridian Green on the colour wheel See Bright Green on the colour wheel
All matches: Viridian Green equivalents · Bright Green equivalents