Process for producing polymeric layers having selectively coloured regions

Process for forming a selectively colored polymeric layer, or a three-dimensional article made of polymeric layers, wherein a photocurable, photocolorable composition is irradiated with a low dose of light to cure and a different, preferably higher, dose of light to color. The process is particularly useful for preparing selectively colored ornamental and industrial articles and models of plant and animal parts, especially medical models.