A-18f Light Grey-Blue vs Underhive Ash

How close are they?

ΔE 14.1, fair: the same colour family, but not a straight swap. Underhive Ash is a little lighter, warmer than A-18f Light Grey-Blue.

Can I use Underhive Ash instead of A-18f Light Grey-Blue?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Underhive Ash is a little lighter, warmer than A-18f Light Grey-Blue.

Can I use A-18f Light Grey-Blue instead of Underhive Ash?

The same difference applies the other way round: A-18f Light Grey-Blue is a little darker, 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.