Runic Cobalt vs Wolven Grey

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Wolven Grey is noticeably lighter, more muted than Runic Cobalt.

Can I use Wolven Grey instead of Runic Cobalt?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Wolven Grey is noticeably lighter, more muted than Runic Cobalt.

Can I use Runic Cobalt instead of Wolven Grey?

The same difference applies the other way round: Runic Cobalt is noticeably darker, 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.