ΔE 8.0, close: similar, with a visible difference side by side. Ulthuan Grey is more saturated than Light Grey. They are different kinds of paint: AMMO by Mig Light Grey is an ink, glaze or transparent paint and Citadel Ulthuan Grey is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Ulthuan Grey is more saturated than Light Grey. They are different kinds of paint.
The same difference applies the other way round: Light Grey is 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.
See Light Grey on the colour wheel See Ulthuan Grey on the colour wheel
All matches: Light Grey equivalents · Ulthuan Grey equivalents