Ferocious Green vs Elixir Green

How close are they?

ΔE 16.0, loose: different enough that you should pick on purpose. Elixir Green is a little lighter, more muted, cooler than Ferocious Green.

Can I use Elixir Green instead of Ferocious Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Elixir Green is a little lighter, more muted, cooler than Ferocious Green.

Can I use Ferocious Green instead of Elixir Green?

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