Forest of Shadows vs Sons of Horus Green

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Sons of Horus Green is a little darker than Forest of Shadows.

Can I use Sons of Horus Green instead of Forest of Shadows?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Sons of Horus Green is a little darker than Forest of Shadows.

Can I use Forest of Shadows instead of Sons of Horus Green?

The same difference applies the other way round: Forest of Shadows is a little lighter.

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.