Shieldwall Blue vs Wolven Grey

How close are they?

ΔE 31.8, loose: different enough that you should pick on purpose. Wolven Grey is noticeably lighter, much more muted than Shieldwall Blue.

Can I use Wolven Grey instead of Shieldwall Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Wolven Grey is noticeably lighter, much more muted than Shieldwall Blue.

Can I use Shieldwall Blue instead of Wolven Grey?

The same difference applies the other way round: Shieldwall Blue is noticeably 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.