ΔE 9.4, close: similar, with a visible difference side by side. Buff is a little darker, more muted than Sand Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Buff is a little darker, more muted than Sand Yellow.
The same difference applies the other way round: Sand Yellow is a little lighter, 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.
See Sand Yellow on the colour wheel See Buff on the colour wheel
All matches: Sand Yellow equivalents · Buff equivalents