ΔE 11.3, fair: the same colour family, but not a straight swap. Transparent Magenta is a little darker, cooler than Blood Chalice. They are different kinds of paint: Army Painter Blood Chalice is an opaque base/layer paint and Green Stuff World Transparent Magenta is an ink, glaze or transparent 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 11). Transparent Magenta is a little darker, cooler than Blood Chalice. They are different kinds of paint.
The same difference applies the other way round: Blood Chalice is a little lighter, 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 Blood Chalice on the colour wheel See Transparent Magenta on the colour wheel
All matches: Blood Chalice equivalents · Transparent Magenta equivalents