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Use drops of b'Lure to colour cocktails. If other ingredients with a higher acidity are added (e.g. citrus juice) the colour changes from blue to purple and pink depending on the colour and acidity (pH) of the drink or food added.

The makers explain, "More Acid = More Purple
The natural colour is blue, ranging from pH 8 to pH 4 (if added to neutral substances like water, clear spirits or milk). b'Lure colour changes to royal purple at pH 3 and to bright pink at pH 2. So, it becomes more acidic by adding other ingredients."