ΔE 9.9, close: similar, with a visible difference side by side. Deck Grey is a little lighter, more muted, warmer than Morghast Bone.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Deck Grey is a little lighter, more muted, warmer than Morghast Bone.
The same difference applies the other way round: Morghast Bone is a little darker, more saturated, 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 Morghast Bone on the colour wheel See Deck Grey on the colour wheel
All matches: Morghast Bone equivalents · Deck Grey equivalents