Warpstone Glow vs Fallen Grass

How close are they?

ΔE 49.1, loose: different enough that you should pick on purpose. Fallen Grass is noticeably darker, much more muted, cooler than Warpstone Glow.

Can I use Fallen Grass instead of Warpstone Glow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 49). Fallen Grass is noticeably darker, much more muted, cooler than Warpstone Glow.

Can I use Warpstone Glow instead of Fallen Grass?

The same difference applies the other way round: Warpstone Glow is noticeably lighter, much 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.