The presented study examines the question of colour categorization in relation to the hypothesis of linguistic relativity. The study is based on research conducted by Gilbert et al. (2006) and their claim that linguistic colour categorization in a particular language helps colour recognition and speeds the process of colour discrimination for colours from different linguistic categories but only for the right visual field. Our study approached the research question differently. We used the same methodology as Gilbert's team et al. (2006), but we used different colour categories in the Czech language and significantly enlarged the number of participants to 106 undergraduate psychology students. Our results show that the fastest reaction times were in trials when the target was located in the left visual field, quite opposite from the Gilbert's et al. (2006) study. We argue that this finding is based on different processes than simple colour linguistic categorisation and attentional processes actually play an important role in the task.