In adults, visual search for a colour target is facilitated if the target and distractors fall in different colour categories (e.g. Daoutis, Pilling, & Davies, in press). The present study explored category effects in children's colour search. The relationship between linguistic colour categories and perceptual categories was addressed by comparing native speakers of languages differing in the number of colour terms. Experiment 1 compared English and Kwanyama (Namibian) children aged 4 to 7 years on a visual search task, using target-distractor pairs (blue-green, blue-purple, red-pink) for which the Kwanyama did not have distinct names. The presence of a category advantage in the English, but not in the Kwanyama, suggested that linguistic boundaries may affect search performance. Experiment 2 examined visual search performance in the green-yellow and the blue-green region, in English and Himba (Namibian) 6-year-olds. The number of distractors was varied to assess search efficiency. Cross-category search was more efficient than within-category search in the English group, but this advantage was absent in the Himba. Increasing the number of distractors affected search speed in the English group, but not in the Himba. Overall, these findings suggest cross-language differences in categorical effects on colour search, but also in the way the children performed the search. The nature of the category effect in search is discussed with respect to these findings.