ΔE 21.8, loose: different enough that you should pick on purpose. Viridian Green is noticeably lighter, much more muted, cooler than Straken Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Viridian Green is noticeably lighter, much more muted, cooler than Straken Green.
The same difference applies the other way round: Straken Green is noticeably darker, 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 Straken Green on the colour wheel See Viridian Green on the colour wheel
All matches: Straken Green equivalents · Viridian Green equivalents