Colored, magnetically attractable powder containing fluorescent dye

A colored powder, particularly a toner powder, containing a thermoplastic resin, a fluorescent dye, possibly a magnetically attractable material and a compound of a metal of which an ion is diagmagnetic. The metal is, for example, calcium, silver, sodium, potassium, barium, aluminium, zirconium, zinc or magnesium. The metal compound is preferably a metal salt and is preferably present in the colored powder in a quantity of between 2 to 15% by weight. Advantageously, the metal compound is dissolved in the thermoplastic resin (or mixture of thermoplastic resins) or be very finely distributed therein. Metal salts, particularly zinc and magnesium salts, of aliphatic, possibly branched carboxylic acids, particularly carboxylic acids having a hydrocarbon radical with at least six carbon atoms, are preferred. The addition of the metal compound reduces extinction of the fluorescence of the fluorescent dye.