Moonstone Grey vs Light Blue RLM78

How close are they?

ΔE 12.2, fair: the same colour family, but not a straight swap. Light Blue RLM78 is a little darker, more saturated than Moonstone Grey.

Can I use Light Blue RLM78 instead of Moonstone Grey?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Light Blue RLM78 is a little darker, more saturated than Moonstone Grey.

Can I use Moonstone Grey instead of Light Blue RLM78?

The same difference applies the other way round: Moonstone Grey is a little lighter, 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.