ΔE 7.7, close: similar, with a visible difference side by side. Sand is more muted, cooler than Monster Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sand is more muted, cooler than Monster Brown.
The same difference applies the other way round: Monster Brown is more saturated, 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 Monster Brown on the colour wheel See Sand on the colour wheel
All matches: Monster Brown equivalents · Sand equivalents