This paper presents the impact of text and background colour combinations on the legibility of characters and readability of text presented on video display units (VDUs). The stimulus features influencing the operator’s response latency and accuracy are analysed in two experiments, examining the effects of text–background colour combinations and stimulus exposition on the ability of character and word identification on VDUs. This is analysed for the purpose of improving the information presentation in control information systems in Serbian underground coal mines. The legibility of characters based on the main colour combinations was tested by focusing on 30 participants. The first experiment required the participants to identify the legibility of uppercase alphabetic characters and numbers randomly selected and presented on a VDU. The visual performance was expressed by the number of correctly identified characters. The second experiment required the participants to identify the readability of the presented characters, based on the colour combinations of the characters and the background, in order to identify the best possible combination of colours for fast identification of information, which is very important in the detection of fast-changing unwanted events. The results of the experiments suggested that the character recognition was strongly influenced by character/background colour combination and exposition. The adequate selection of these variables can significantly improve the legibility of characters, and improve the speed and the accuracy of the identification of potential problems in underground coal mines during emergency situations.