ΔE 14.1, fair: the same colour family, but not a straight swap. Light Phthalo Blue is a little lighter, more saturated than Blue Horror.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Light Phthalo Blue is a little lighter, more saturated than Blue Horror.
The same difference applies the other way round: Blue Horror is a little darker, more muted.
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 Blue Horror on the colour wheel See Light Phthalo Blue on the colour wheel
All matches: Blue Horror equivalents · Light Phthalo Blue equivalents