Forest Green vs Guardian Green

How close are they?

ΔE 6.4, close: similar, with a visible difference side by side. Guardian Green is a little lighter, cooler than Forest Green.

Can I use Guardian Green instead of Forest Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Guardian Green is a little lighter, cooler than Forest Green.

Can I use Forest Green instead of Guardian Green?

The same difference applies the other way round: Forest 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.