Engineering plastics, especially polyamide, are coloured with improved fastness and stability properties using pigment compositions comprising an organic pigment wholly overlaid with a crosslinked (meth)acrylic resin or copolymer thereof. Preference is given to the use of diketopyrrolopyrrole, azo, pteridine, isoindoline and isoindolinone pigments. Processes for the preparation of the pigment compositions are also claimed.