ΔE 8.9, close: similar, with a visible difference side by side. Parched Grass (Late) is a little darker, warmer than Bastion Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Parched Grass (Late) is a little darker, warmer than Bastion Grey.
The same difference applies the other way round: Bastion Grey 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 Bastion Grey on the colour wheel See Parched Grass (Late) on the colour wheel
All matches: Bastion Grey equivalents · Parched Grass (Late) equivalents