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Colour and Luminosity Measurement Tools to Improve Accessibility


Measurement of colour contrast and luminosity is key in assisting people with low vision to navigate both built environments and the world wide web.

Roger Johansson a web engineer put together a very helpful web page entitled 10 colour contrast checking tools to improve the accessibility of your design. Roger made the point that "It is important to understand that there are different algorithms used to calculate contrast ratios. Some tools use the luminosity contrast ratio algorithm mentioned by the WCAG (Web Content Accessibility Guidelines) 2.0 working draft, while others use the colour brightness and colour difference algorithms."

An updated list of useful tools is given below based on Roger's orginal list:

  • Colour Contrast Check: The Colour Contrast Check Tool allows to specify a foreground and a background colour and determine if they provide enough of a contrast "when viewed by someone having color deficits or when viewed on a black and white screen"[W3C].
  • Luminosity Contrast Ratio Analyser: This tool, tests foreground and background colour combinations according to WCAG 2.0's luminosity contrast algorithm.
  • Vischeck: Vischeck is a way of showing you what things look like to someone who is color blind. You can try Vischeck online- either run Vischeck on your own image files or run Vischeck on a web page. You can also download programs to let you run it on your own computer.
  • Colour Contrast Analyser: Vision Australia's Colour Contrast Analyser is compatible with the Web Content Accessibility Guidelines version 2 (WCAG 2.0). The tool was developed by the Web Accessibility Tools Consortium in collaboration with Vision Australia and Steve Faulkner of The Paciello Group (Europe).
  • Graybit: Relying on colors to determine page visibility and contrast can be misleading. Converting the colors to their grayscale equivalents is a more reliable method. By removing color’s influence, you’ll better find true visual contrast,
  • Sim Daltonism: Available for Mac OS X only, this standalone application does not calculate colour contrast, but is still very useful. It simulates various kinds of colour blindness in realtime, which makes it easy to check if a design is likely to cause problems.
  • Color Oracle: Color Oracle is a free color blindness simulator for Window, Mac and Linux. It takes the guesswork out of designing for color blindness by showing you in real time what people with common color vision impairments will see.


While none of the above are intended for the built environment some can be used with photographs or a new measuremt tool called the CUBE, this is a colour sampling tool linked to an App for ios and Android smart devices.This device when paired to the Cube's amtching Companion App can record, tag and share captured colors. It then reveal detailed color information which can dovetail with the above tools) and is matched to the world’s best paint and color databases. This very helpful information can be used to improve colour, contrast and perception for internal built environments. More detail can be found within the Colour, light and contrast manual: Designing for and Managing Inclusive Built Environments book authored by Bright and Cook in 2010.

As explained within the same book "the ways colour, light and contrast are used within built environments [is] critical in determining how people interact with the space, and how confident, safe, and secure [people] they will feel when doing so. ... Understanding how to use colour and contrast and how they are influenced by both natural and artificial lighting is vital for all those involved in the design and management of the environments and spaces we all use".


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