ΔE 19.2, loose: different enough that you should pick on purpose. Flat Yellow is a little lighter, cooler than Pure Orange.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Flat Yellow is a little lighter, cooler than Pure Orange.
The same difference applies the other way round: Pure Orange is a little darker, 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 Pure Orange on the colour wheel See Flat Yellow on the colour wheel
All matches: Pure Orange equivalents · Flat Yellow equivalents