ΔE 12.1, fair: the same colour family, but not a straight swap. Flash Gitz Yellow is more saturated than Fluorescent Yellow. They are different kinds of paint: AK Interactive Fluorescent Yellow is a fluorescent or effect paint and Citadel Flash Gitz Yellow is an opaque base/layer 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). Flash Gitz Yellow is more saturated than Fluorescent Yellow. They are different kinds of paint.
The same difference applies the other way round: Fluorescent Yellow is more muted.
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 Fluorescent Yellow on the colour wheel See Flash Gitz Yellow on the colour wheel
All matches: Fluorescent Yellow equivalents · Flash Gitz Yellow equivalents