Mortarion Green Clear vs Bright Green

How close are they?

ΔE 9.3, close: similar, with a visible difference side by side. Bright Green is cooler than Mortarion Green Clear.

Can I use Bright Green instead of Mortarion Green Clear?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Bright Green is cooler than Mortarion Green Clear.

Can I use Mortarion Green Clear instead of Bright Green?

The same difference applies the other way round: Mortarion Green Clear is 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.