ΔE 14.5, fair: the same colour family, but not a straight swap. Manganese Blue Hue is noticeably lighter, more saturated, cooler than Frostheart. They are different kinds of paint: Citadel Frostheart is a one-coat contrast-style paint and Golden Manganese Blue Hue is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Manganese Blue Hue is noticeably lighter, more saturated, cooler than Frostheart. They are different kinds of paint.
The same difference applies the other way round: Frostheart is noticeably darker, more muted, warmer.
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 Frostheart on the colour wheel See Manganese Blue Hue on the colour wheel
All matches: Frostheart equivalents · Manganese Blue Hue equivalents