Icy Grey vs Sky Blue

How close are they?

ΔE 22.7, loose: different enough that you should pick on purpose. Sky Blue is a little lighter, much more saturated than Icy Grey.

Can I use Sky Blue instead of Icy Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sky Blue is a little lighter, much more saturated than Icy Grey.

Can I use Icy Grey instead of Sky Blue?

The same difference applies the other way round: Icy Grey is a little darker, 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.