Hazardous Smog vs Light Blue

How close are they?

ΔE 27.3, loose: different enough that you should pick on purpose. Light Blue is a little lighter, much more muted, cooler than Hazardous Smog.

Can I use Light Blue instead of Hazardous Smog?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Light Blue is a little lighter, much more muted, cooler than Hazardous Smog.

Can I use Hazardous Smog instead of Light Blue?

The same difference applies the other way round: Hazardous Smog is a little darker, much more saturated, warmer.

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.