Trial archaeological excavations undertaken at the hillfort of Sveta Trojica (Holy Trinity), situated on the Adriatic coast of Croatia, yielded significant amounts of pottery and several metal finds, including coins dating between the 4th and the end of the 1st century BC. The settlement is attributed to the autochthonous, protohistoric Liburnian community. Early Roman artefacts were found on the slopes closer to the sea shore, including an interesting grave of an auxiliary soldier of the late Augustan-early Tiberian period. The site includes a Byzantine fortress in the area between the protohistoric settlement and the sea shore. A curious superficial layer of crushed shells has been observed on the western slopes of the hillfort. This consists of Muricidae shells, heavily fragmented and obviously deliberately crushed. This paper examines the possibility that these shell remains indicate small-scale dye production alongside evidence of dye production on the Eastern Adriatic coast during the Roman period, and from information recorded by ancient sources that describe textile production among the Liburni, and will present possible new approaches and discuss the possibilities of protohistoric dye production.