PURPOSE: To provide the subject pigment capable of decoloring or color changing with light having a wavelength different from that of light curing a solder resist agent and of accurately forming characters, signals, etc., excellent in reproducibility, thermal stability in after treatment and shelf life.

CONSTITUTION: The objective pigment is represented by formula I [X1 and X2 are each H, nitro, cyano, etc.; Y1 and Y2 are each an alkoxy, an acylamino, Cl, etc.; R1 and R2 are each a (substituted)alkyl], used by blending with a solder resist agent curable by exposure to light of a prescribed wavelength and capable of decoloring or color changing by exposure to light of a wavelength different from that of light curing the above-mentioned solder resist agent. As the above- mentioned pigment, a compound of formula II is exemplified. The above- mentioned solder resist agent is generally composed of an unsaturated bond- containing resin, a reactive diluent, a photoreaction initiator, etc. As the above- mentioned resin, an epoxy acrylate, etc., is used. 2-Hydroxymethyl (meth) acrylate, etc., and biacetyl, etc., are used respectively as the reaction diluent and the photoreaction initiator.