Cloudburst Blue vs Graphite Grey

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Graphite Grey is a little darker, much more muted than Cloudburst Blue.

Can I use Graphite Grey instead of Cloudburst Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Graphite Grey is a little darker, much more muted than Cloudburst Blue.

Can I use Cloudburst Blue instead of Graphite Grey?

The same difference applies the other way round: Cloudburst 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.