Underhive Ash vs Sky BS381C/210

How close are they?

ΔE 14.6, fair: the same colour family, but not a straight swap. Sky BS381C/210 is a little lighter, much more saturated, cooler than Underhive Ash.

Can I use Sky BS381C/210 instead of Underhive Ash?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Sky BS381C/210 is a little lighter, much more saturated, cooler than Underhive Ash.

Can I use Underhive Ash instead of Sky BS381C/210?

The same difference applies the other way round: Underhive Ash is a little darker, much more muted, 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.