ΔE 13.4, fair: the same colour family, but not a straight swap. Hexwraith Flame is much more saturated, cooler than Mecha Light Green. They are different kinds of paint: AMMO by Mig Mecha Light Green is an opaque base/layer paint and Citadel Hexwraith Flame is a one-coat contrast-style paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Hexwraith Flame is much more saturated, cooler than Mecha Light Green. They are different kinds of paint.
The same difference applies the other way round: Mecha Light Green is much more muted, 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 Mecha Light Green on the colour wheel See Hexwraith Flame on the colour wheel
All matches: Mecha Light Green equivalents · Hexwraith Flame equivalents