Fluorescent Red vs Vomit

How close are they?

ΔE 56.6, loose: different enough that you should pick on purpose. Vomit is noticeably lighter, much more muted, warmer than Fluorescent Red.

Can I use Vomit instead of Fluorescent Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 57). Vomit is noticeably lighter, much more muted, warmer than Fluorescent Red.

Can I use Fluorescent Red instead of Vomit?

The same difference applies the other way round: Fluorescent Red is noticeably darker, much more saturated, 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.