ΔE 16.6, loose: different enough that you should pick on purpose. Fluorescent Blue is a little lighter, much more saturated, warmer than Baharroth Blue. They are different kinds of paint: Citadel Baharroth Blue is an opaque base/layer paint and Golden Fluorescent Blue is a fluorescent or effect paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Fluorescent Blue is a little lighter, much more saturated, warmer than Baharroth Blue. They are different kinds of paint.
The same difference applies the other way round: Baharroth Blue is a little darker, much more muted, cooler.
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 Baharroth Blue on the colour wheel See Fluorescent Blue on the colour wheel
All matches: Baharroth Blue equivalents · Fluorescent Blue equivalents