Emerald Forest vs Iosan Green

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Iosan Green is more muted, cooler than Emerald Forest.

Can I use Iosan Green instead of Emerald Forest?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Iosan Green is more muted, cooler than Emerald Forest.

Can I use Emerald Forest instead of Iosan Green?

The same difference applies the other way round: Emerald Forest is 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.