ΔE 15.5, loose: different enough that you should pick on purpose. A-28M Greyish Blue is more saturated, warmer than Frost Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). A-28M Greyish Blue is more saturated, warmer than Frost Blue.
The same difference applies the other way round: Frost Blue is 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.
See Frost Blue on the colour wheel See A-28M Greyish Blue on the colour wheel
All matches: Frost Blue equivalents · A-28M Greyish Blue equivalents