The use of colour to emphasise important information and headings of package leaflets has been recommended in the readability guideline of the European Union since 1998. Our study investigated the advantages and disadvantages of coloured and black/greyscale versions.

Package leaflets, created for three different medicines, each using two templates of different lengths (a 200-word template and the QRD template), were printed once in colour and once in black font with greyscale illustrations. Using the written readability test, 192 participants located the information and answered 25 content questions over a timescale of 20 minutes (calculated median).

The only significant advantage uncovered for either design option occurred in the case of coloured versions using the 200-word template, with participants causing less errors (12.1 % not found or incorrect answer) than in the black/greyscale versions (18.7 %). On the other hand, patients tended to require less time to locate information when using only black font on white background; however, this was not significant. Therefore, both design options – coloured and black/greyscale – are appropriate for package leaflets (PDF).