A Contrast Colour Selection Scheme for WCAG2.0-Compliant Web Designs Based on HSV-Half-Planes

Sufficient colour contrast between text and background is necessary for the text to be readable. WCAG2.0 defines contrast guidelines that ensure web pages can be read by people with a visual acuity of as low as 20/80. However, the WCAG2.0 specification is hard to understand for web-designers and they often perform colour checks after the design is finished using colour contrast calculators. It is then often too late to make significant changes to the design. This paper proposes a new colour selection scheme that integrates contrast constraints into the main design phase by only allowing designers to select colour pairs that contains sufficient contrast. The mechanism is compatible with the colour harmony systems commonly used by designers. The tool gives designers an easily perceivable overview of the design space of available colours. The paper briefly describes a prototype of a colour picker tool that implements the proposed scheme.