ΔE 18.1, loose: different enough that you should pick on purpose. Flat Yellow is noticeably darker, more saturated, warmer than Vanilla Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Flat Yellow is noticeably darker, more saturated, warmer than Vanilla Yellow.
The same difference applies the other way round: Vanilla Yellow is noticeably lighter, more muted, 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.
See Vanilla Yellow on the colour wheel See Flat Yellow on the colour wheel
All matches: Vanilla Yellow equivalents · Flat Yellow equivalents