Dark Green Blue vs Troll Green

How close are they?

ΔE 30.5, loose: different enough that you should pick on purpose. Troll Green is a little lighter, much more saturated, warmer than Dark Green Blue.

Can I use Troll Green instead of Dark Green Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Troll Green is a little lighter, much more saturated, warmer than Dark Green Blue.

Can I use Dark Green Blue instead of Troll Green?

The same difference applies the other way round: Dark Green Blue is a little darker, much more muted, cooler.

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.