ΔE 10.9, fair: the same colour family, but not a straight swap. Cement Grey is a little lighter, cooler than Bastion Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Cement Grey is a little lighter, cooler than Bastion Grey.
The same difference applies the other way round: Bastion Grey is a little darker, 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 Bastion Grey on the colour wheel See Cement Grey on the colour wheel
All matches: Bastion Grey equivalents · Cement Grey equivalents