Dusty Blue vs Landser Grey

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Landser Grey is a little darker, much more muted than Dusty Blue.

Can I use Landser Grey instead of Dusty Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Landser Grey is a little darker, much more muted than Dusty Blue.

Can I use Dusty Blue instead of Landser Grey?

The same difference applies the other way round: Dusty Blue is a little lighter, 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.