ΔE 11.9, fair: the same colour family, but not a straight swap. Light Green RLM25 is cooler than Fallen Grass.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Light Green RLM25 is cooler than Fallen Grass.
The same difference applies the other way round: Fallen Grass 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.
See Fallen Grass on the colour wheel See Light Green RLM25 on the colour wheel
All matches: Fallen Grass equivalents · Light Green RLM25 equivalents