Orange Neon vs Vomit

How close are they?

ΔE 39.8, loose: different enough that you should pick on purpose. Vomit is noticeably lighter, more muted than Orange Neon.

Can I use Vomit instead of Orange Neon?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Vomit is noticeably lighter, more muted than Orange Neon.

Can I use Orange Neon instead of Vomit?

The same difference applies the other way round: Orange Neon is noticeably darker, 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.