Fluorescent Orange-Yellow vs Vomit

How close are they?

ΔE 35.1, loose: different enough that you should pick on purpose. Vomit is noticeably lighter, much more muted than Fluorescent Orange-Yellow.

Can I use Vomit instead of Fluorescent Orange-Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 35). Vomit is noticeably lighter, much more muted than Fluorescent Orange-Yellow.

Can I use Fluorescent Orange-Yellow instead of Vomit?

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

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.