ΔE 22.6, loose: different enough that you should pick on purpose. Pearl Light Blue is much more saturated than Ironbreaker. They are different kinds of paint: Citadel Ironbreaker is a metallic and Tamiya Pearl Light Blue is a pearl paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Pearl Light Blue is much more saturated than Ironbreaker. They are different kinds of paint.
The same difference applies the other way round: Ironbreaker is much 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 Ironbreaker on the colour wheel See Pearl Light Blue on the colour wheel
All matches: Ironbreaker equivalents · Pearl Light Blue equivalents