ΔE 12.3, fair: the same colour family, but not a straight swap. Sky Blue is a little lighter, more saturated than RLM 78 Light Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Sky Blue is a little lighter, more saturated than RLM 78 Light Blue.
The same difference applies the other way round: RLM 78 Light Blue 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 RLM 78 Light Blue on the colour wheel See Sky Blue on the colour wheel
All matches: RLM 78 Light Blue equivalents · Sky Blue equivalents