ΔE 7.6, close: similar, with a visible difference side by side. Sand is a little lighter, warmer than Red Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sand is a little lighter, warmer than Red Grey.
The same difference applies the other way round: Red Grey is a little darker, 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 Red Grey on the colour wheel See Sand on the colour wheel
All matches: Red Grey equivalents · Sand equivalents