Medieval Forest vs Kabalite Green

How close are they?

ΔE 17.0, loose: different enough that you should pick on purpose. Kabalite Green is a little lighter, much more saturated than Medieval Forest.

Can I use Kabalite Green instead of Medieval Forest?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Kabalite Green is a little lighter, much more saturated than Medieval Forest.

Can I use Medieval Forest instead of Kabalite Green?

The same difference applies the other way round: Medieval Forest is a little darker, much more muted.

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.