ΔE 21.8, loose: different enough that you should pick on purpose. Frost is a little lighter, much more muted, cooler than Fluorescent Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Frost is a little lighter, much more muted, cooler than Fluorescent Blue.
The same difference applies the other way round: Fluorescent Blue is a little darker, 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 Blue on the colour wheel See Frost on the colour wheel
All matches: Fluorescent Blue equivalents · Frost equivalents