ΔE 8.2, close: similar, with a visible difference side by side. Dark Sand is more saturated than Middle Stone.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Dark Sand is more saturated than Middle Stone.
The same difference applies the other way round: Middle Stone is more muted.
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 Middle Stone on the colour wheel See Dark Sand on the colour wheel
All matches: Middle Stone equivalents · Dark Sand equivalents