Plasma Coil Glow vs Spectral Blue

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Spectral Blue is noticeably darker, more muted, warmer than Plasma Coil Glow.

Can I use Spectral Blue instead of Plasma Coil Glow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Spectral Blue is noticeably darker, more muted, warmer than Plasma Coil Glow.

Can I use Plasma Coil Glow instead of Spectral Blue?

The same difference applies the other way round: Plasma Coil Glow is noticeably lighter, more saturated, 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.