ΔE 16.6, loose: different enough that you should pick on purpose. Walnut is a little darker, more muted, warmer than Desert Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Walnut is a little darker, more muted, warmer than Desert Yellow.
The same difference applies the other way round: Desert Yellow is a little lighter, 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.
See Desert Yellow on the colour wheel See Walnut on the colour wheel
All matches: Desert Yellow equivalents · Walnut equivalents