Toxic Mist vs Scaly Highlight

How close are they?

ΔE 28.3, loose: different enough that you should pick on purpose. Scaly Highlight is noticeably darker, more saturated, warmer than Toxic Mist.

Can I use Scaly Highlight instead of Toxic Mist?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Scaly Highlight is noticeably darker, more saturated, warmer than Toxic Mist.

Can I use Toxic Mist instead of Scaly Highlight?

The same difference applies the other way round: Toxic Mist is noticeably lighter, more muted, cooler.

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.