Readability of text is strongly influenced by the contrast between text and background. A high contrast makes it easier to absorb information. Therefore complementary colours are ideal with black text on a white background being most preferred. The reviewed literature showed a definite dislike of both yellow on red and the black on red colour combinations. A black font written on white contrast was easiest to read.
These guidelines were followed in the development of the prototype through all stages and they proved to be acceptable. Red, green and blue fonts on white contrast were used in the prototype through all stages to highlight importance such as the word “risk”.
The Stakeholders advised to consider the impact of having a “yellow zone” in the graph to indicate a normal zone. Whether this encouraged inaction was later investigated in the patients’ focus groups and was found to be relevant to the English speakers group while the CALD groups preferred to have only two–colour zones. Overall, the feeling was that the use of colours was helpful and makes the report attractive compared to a black and white report.
The research team limited the number of colours in the graph to two colours based on compromising the results of the focus groups of patients. In the GP trial, one third of healthcare professionals stated that the colours were the most useful part in the report.
Therefore, it is advisable to use various colors in presenting the information and graph zones in the report. It is essential though not to rely on colour (especially the popular red and green) alone to convey information since 10% of the male population is red-green colour blind. This has been achieved by including a textual description of the brackets (“too high”, “healthy”, “too low”) in the graph.