Castellan Green vs Forest Green

How close are they?

ΔE 6.9, close: similar, with a visible difference side by side. Forest Green is a little darker, cooler than Castellan Green.

Can I use Forest Green instead of Castellan Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Forest Green is a little darker, cooler than Castellan Green.

Can I use Castellan Green instead of Forest Green?

The same difference applies the other way round: Castellan Green is a little lighter, 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.