Frog Green vs Mortarion Green Clear

How close are they?

ΔE 22.9, loose: different enough that you should pick on purpose. Mortarion Green Clear is noticeably darker, more muted, cooler than Frog Green.

Can I use Mortarion Green Clear instead of Frog Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Mortarion Green Clear is noticeably darker, more muted, cooler than Frog Green.

Can I use Frog Green instead of Mortarion Green Clear?

The same difference applies the other way round: Frog Green is noticeably lighter, 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.