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