The present invention provides a one-liquid low temperature hardenable type colored enamel paint and a one-liquid low temperature hardenable type clear paint, which are used for coating of plastic materials and sufficiently harden even by baking at a low temperature and can form a hardened coating film that is excellent in contaminationproofing and acidproofing without damaging flexibility. The colored enamel paint comprises: resin components, which include a polyesterpolyol and an acrylic polyol; a crosslinking agent, which includes a blocked isocyanate as the essential component and may further include a melamine resin; a blocked isocyanate dissociation catalyst, which at least includes a dibutyltin dicarboxylate; and a pigment. The clear paint comprises: a resin component, which includes an acrylic polyol; the crosslinking agent; and the blocked isocyanate dissociation catalyst.