Ultimate Cup of Coffee vs Dark Blue RLM24

How close are they?

ΔE 21.7, loose: different enough that you should pick on purpose. Dark Blue RLM24 is a little darker, much more saturated than Ultimate Cup of Coffee.

Can I use Dark Blue RLM24 instead of Ultimate Cup of Coffee?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Dark Blue RLM24 is a little darker, much more saturated than Ultimate Cup of Coffee.

Can I use Ultimate Cup of Coffee instead of Dark Blue RLM24?

The same difference applies the other way round: Ultimate Cup of Coffee is a little lighter, much 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.