ΔE 9.7, close: similar, with a visible difference side by side. Fluor Yellow is a little lighter, cooler than Dorn Yellow. They are different kinds of paint: Citadel Dorn Yellow is an opaque base/layer paint and Green Stuff World Fluor Yellow is a fluorescent or effect paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Fluor Yellow is a little lighter, cooler than Dorn Yellow. They are different kinds of paint.
The same difference applies the other way round: Dorn Yellow is a little darker, 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 Dorn Yellow on the colour wheel See Fluor Yellow on the colour wheel
All matches: Dorn Yellow equivalents · Fluor Yellow equivalents