Acid Green vs Orc Skin

How close are they?

ΔE 6.8, close: similar, with a visible difference side by side. Orc Skin is a little lighter, cooler than Acid Green.

Can I use Orc Skin instead of Acid Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Orc Skin is a little lighter, cooler than Acid Green.

Can I use Acid Green instead of Orc Skin?

The same difference applies the other way round: Acid Green is a little darker, 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.