Wolven Grey vs Medium Grey Blue

How close are they?

ΔE 20.9, loose: different enough that you should pick on purpose. Medium Grey Blue is noticeably darker, more saturated than Wolven Grey.

Can I use Medium Grey Blue instead of Wolven Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Medium Grey Blue is noticeably darker, more saturated than Wolven Grey.

Can I use Wolven Grey instead of Medium Grey Blue?

The same difference applies the other way round: Wolven Grey is noticeably 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.