ΔE 50.0, loose: different enough that you should pick on purpose. Umber Wash is a little lighter, much more muted, warmer than Biel-Tan Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 50). Umber Wash is a little lighter, much more muted, warmer than Biel-Tan Green.
The same difference applies the other way round: Biel-Tan Green is a little darker, 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 Biel-Tan Green on the colour wheel See Umber Wash on the colour wheel
All matches: Biel-Tan Green equivalents · Umber Wash equivalents