ΔE 19.2, loose: different enough that you should pick on purpose. Sons of Horus Green is noticeably darker, warmer than Spectral Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Sons of Horus Green is noticeably darker, warmer than Spectral Blue.
The same difference applies the other way round: Spectral Blue is noticeably lighter, 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.
See Spectral Blue on the colour wheel See Sons of Horus Green on the colour wheel
All matches: Spectral Blue equivalents · Sons of Horus Green equivalents