Colour blindness is the inability to perceive differences between some or all colours that other people can distinguish. It is most often of genetic nature but may also occur because of eye, nerve or brain damage or due to exposure to some chemicals. The most common type of colour vision deficiency is red-green colour blindness. Types of red-green colour blindness include pro-tanopia, deuteranopia, protanomalia and deuteranomalia which denote lack of ability to distin-guish between colours in the green-yellow-red section of the spectrum in addition to abnormal diming, lack of ability to distinguish between colours in the green-yellow-red section of the spec-trum but without abnormal diming, less sensitivity to red and weakness in perception of green respectively. This study investigated the prevalence and impact of colour blindness on the study of science and on Information and Communication Technologies (ICTs) usage such as com-puter usage and internet browsing. The study participants were science students aged between fifteen and twenty-three whose courses such as Chemistry and Biology require identification, naming and matching of colours. The study was done using the Ishihara 24 plate edition which the participants examined and the numerals identified were recorded without more than three seconds delay. Questionnaires were administered to participants who tested positive for colour blindness. Out of 1194 male students sampled, 1.2% were colour blind. None of the 566 females included in the study was colour blind. Twelve (12) of the male participants were either deuter-anopes, strong deuteranomalous, mild protanomalous, mild deuteranomalous, protanopes or strong protanomalous while 2 students had other forms of red-green colour blindness that could not be classified with the Ishihara plates. The deutan type was the most common red-green defi-ciency in this study accounting for 64% of all types. There was no significant difference between prevalence of red-green colour blindness at the secondary and tertiary levels (p>0.05). Colour blind students who experienced difficulties in their studies such as difficulties in performing practicals and internet browsing that require them to identify, name or discriminate colours, managed these difficulties by employing the help of their mates. The results suggest that red-green colour vision deficiency may influence but does not prevent study of science, computer usage or internet browsing and that some red-green colour blind science students may need help.