Voidshield Blue vs Sky Grey

How close are they?

ΔE 32.6, loose: different enough that you should pick on purpose. Sky Grey is noticeably lighter, much more muted than Voidshield Blue.

Can I use Sky Grey instead of Voidshield Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 33). Sky Grey is noticeably lighter, much more muted than Voidshield Blue.

Can I use Voidshield Blue instead of Sky Grey?

The same difference applies the other way round: Voidshield Blue is noticeably 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.