ΔE 14.5, fair: the same colour family, but not a straight swap. Cool Grey is a little lighter, much more muted than Runic Cobalt.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Cool Grey is a little lighter, much more muted than Runic Cobalt.
The same difference applies the other way round: Runic Cobalt is a little darker, much more saturated.
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 Runic Cobalt on the colour wheel See Cool Grey on the colour wheel
All matches: Runic Cobalt equivalents · Cool Grey equivalents