ΔE 84.1, loose: different enough that you should pick on purpose. Green Rust is noticeably darker, much more muted, cooler than Fluorescent Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 84). Green Rust is noticeably darker, much more muted, cooler than Fluorescent Yellow.
The same difference applies the other way round: Fluorescent Yellow is noticeably lighter, much more saturated, 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 Fluorescent Yellow on the colour wheel See Green Rust on the colour wheel
All matches: Fluorescent Yellow equivalents · Green Rust equivalents