Imperial Navy vs Paynes Gray

How close are they?

ΔE 23.4, loose: different enough that you should pick on purpose. Paynes Gray is a little darker, much more muted than Imperial Navy.

Can I use Paynes Gray instead of Imperial Navy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Paynes Gray is a little darker, much more muted than Imperial Navy.

Can I use Imperial Navy instead of Paynes Gray?

The same difference applies the other way round: Imperial Navy 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.