ΔE 6.7, close: similar, with a visible difference side by side. Transparent Blue is more saturated than Ultramarine Blue. They are different kinds of paint: Army Painter Ultramarine Blue is an opaque base/layer paint and Pro Acryl Transparent Blue is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Transparent Blue is more saturated than Ultramarine Blue. They are different kinds of paint.
The same difference applies the other way round: Ultramarine Blue is 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 Ultramarine Blue on the colour wheel See Transparent Blue on the colour wheel
All matches: Ultramarine Blue equivalents · Transparent Blue equivalents