ΔE 10.4, fair: the same colour family, but not a straight swap. Buff is a little lighter, more saturated, cooler than Medium Sand.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Buff is a little lighter, more saturated, cooler than Medium Sand.
The same difference applies the other way round: Medium Sand is a little darker, more muted, 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 Medium Sand on the colour wheel See Buff on the colour wheel
All matches: Medium Sand equivalents · Buff equivalents