ΔE 9.7, close: similar, with a visible difference side by side. IDF Sand Grey is more muted, cooler than Skeleton Legion.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). IDF Sand Grey is more muted, cooler than Skeleton Legion.
The same difference applies the other way round: Skeleton Legion 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 Skeleton Legion on the colour wheel See IDF Sand Grey on the colour wheel
All matches: Skeleton Legion equivalents · IDF Sand Grey equivalents