ΔE 12.1, fair: the same colour family, but not a straight swap. Fluor Lime is noticeably lighter than Mantis Warriors Green. They are different kinds of paint: Citadel Mantis Warriors Green is a one-coat contrast-style paint and Green Stuff World Fluor Lime is a fluorescent or effect 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 12). Fluor Lime is noticeably lighter than Mantis Warriors Green. They are different kinds of paint.
The same difference applies the other way round: Mantis Warriors Green is noticeably darker.
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 Mantis Warriors Green on the colour wheel See Fluor Lime on the colour wheel
All matches: Mantis Warriors Green equivalents · Fluor Lime equivalents