Cognitive psychologists have discovered different design principles to enhance memory performance. It has been said that retrieving process depends on many variables and one of them is colour. This paper provides an overview of research on colour and learning. It includes the effect of colour on attention, retention and memory performance, and relates these to the design of instructional materials. The study reported the effect colour had on the retention rate of graduate students of the Olabisi Onabanjo University, Ago-Iwoye. Thirty graduate students participated in this study. The purpose of this research study was to determine if colour (in prints form) influence the learning process. The independent variable was colour at two levels: Congruent colours (colours corresponding to the words) and Incongruent colours (colours not related to the words), while for the control, Achromatic colours (black and shades of grey) were used. The dependent variable was the retention rate i.e. number of words recalled. The research design was a posttest only design. A one-way ANOVA was used to analyze the data and the results indicated that there was a statistically significant difference in the number of words recalled based on colour. The groups exposed to congruent colours and achromatic colours performed better than those exposed to incongruent colours, although the group exposed to the congruent colour prints performed better than those of the other groups. Therefore designers of instructional materials need to use colour wisely by paying attention to the effect of colour on learning.