ΔE 7.8, close: similar, with a visible difference side by side. Pastel Indigo is a little lighter, more saturated, warmer than Whale Grey. They are different kinds of paint: AMMO by Mig Whale Grey is an opaque base/layer paint and Army Painter Pastel Indigo is a one-coat contrast-style 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). Pastel Indigo is a little lighter, more saturated, warmer than Whale Grey. They are different kinds of paint.
The same difference applies the other way round: Whale Grey is a little darker, more muted, 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 Whale Grey on the colour wheel See Pastel Indigo on the colour wheel
All matches: Whale Grey equivalents · Pastel Indigo equivalents