This research investigated how German-speaking children learn color words, both in terms of centroid mappings and boundary delineation, and how they construct the color lexicon as a connected system. The results were compared to those of Japanese children to draw insights on general mechanisms that underlie the acquisition of words in the color lexicon. For both languages, input frequency and category size contributed to the ease of learning. In contrast, in both language groups, naming (in)consistency in adults predicted the adult-like boundary delineation.