ΔE 15.6, loose: different enough that you should pick on purpose. Rus. AF Grey Prot. Coat is a little darker, more muted, warmer than Light Phthalo Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Rus. AF Grey Prot. Coat is a little darker, more muted, warmer than Light Phthalo Blue.
The same difference applies the other way round: Light Phthalo Blue is a little 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.
See Light Phthalo Blue on the colour wheel See Rus. AF Grey Prot. Coat on the colour wheel
All matches: Light Phthalo Blue equivalents · Rus. AF Grey Prot. Coat equivalents