Ruinous Spell vs Green

How close are they?

ΔE 11.4, fair: the same colour family, but not a straight swap. Green is a little darker, warmer than Ruinous Spell.

Can I use Green instead of Ruinous Spell?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Green is a little darker, warmer than Ruinous Spell.

Can I use Ruinous Spell instead of Green?

The same difference applies the other way round: Ruinous Spell is a little lighter, 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.