Ocean Depths vs N4 Neutral Gray

How close are they?

ΔE 21.7, loose: different enough that you should pick on purpose. N4 Neutral Gray is a little lighter, much more muted than Ocean Depths.

Can I use N4 Neutral Gray instead of Ocean Depths?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). N4 Neutral Gray is a little lighter, much more muted than Ocean Depths.

Can I use Ocean Depths instead of N4 Neutral Gray?

The same difference applies the other way round: Ocean Depths is a little 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.