ΔE 79.3, loose: different enough that you should pick on purpose. Fluorescent Yellow is noticeably lighter, much more saturated, cooler than Fluor Orange.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 79). Fluorescent Yellow is noticeably lighter, much more saturated, cooler than Fluor Orange.
The same difference applies the other way round: Fluor Orange is noticeably darker, 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 Fluor Orange on the colour wheel See Fluorescent Yellow on the colour wheel
All matches: Fluor Orange equivalents · Fluorescent Yellow equivalents