Warpstone Glow vs Orc Green

How close are they?

ΔE 20.5, loose: different enough that you should pick on purpose. Orc Green is a little darker, much more muted than Warpstone Glow.

Can I use Orc Green instead of Warpstone Glow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Orc Green is a little darker, much more muted than Warpstone Glow.

Can I use Warpstone Glow instead of Orc Green?

The same difference applies the other way round: Warpstone Glow is a little lighter, much more saturated.

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.