ΔE 10.4, fair: the same colour family, but not a straight swap. Foul Green is a little lighter, warmer than Cobalt Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Foul Green is a little lighter, warmer than Cobalt Green.
The same difference applies the other way round: Cobalt Green is a little darker, 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 Cobalt Green on the colour wheel See Foul Green on the colour wheel
All matches: Cobalt Green equivalents · Foul Green equivalents