Light Grey Shadow vs Slaanesh Grey

How close are they?

ΔE 11.2, fair: the same colour family, but not a straight swap. Slaanesh Grey is a little darker, more saturated than Light Grey Shadow.

Can I use Slaanesh Grey instead of Light Grey Shadow?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Slaanesh Grey is a little darker, more saturated than Light Grey Shadow.

Can I use Light Grey Shadow instead of Slaanesh Grey?

The same difference applies the other way round: Light Grey Shadow is a little lighter, more muted.

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.