ΔE 7.9, close: similar, with a visible difference side by side. IAF Sand is a little darker, warmer than Necrolith Bone.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). IAF Sand is a little darker, warmer than Necrolith Bone.
The same difference applies the other way round: Necrolith Bone is a little lighter, 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 Necrolith Bone on the colour wheel See IAF Sand on the colour wheel
All matches: Necrolith Bone equivalents · IAF Sand equivalents