Web tool · reddy.world/ral-contrast-checker
RAL Contrast Checker
Two RAL colours, scored for contrast.
The RAL Contrast Checker shows two RAL colours side by side and scores them for accessibility. Pick a background and an object or text colour, and you see the pair at once, with two numbers: the difference in light reflectance, for the real world, and the WCAG contrast ratio, for screens. Open the checker.
It started as a team assignment for Stichting Accessibility by students of Hogeschool Utrecht in 2023, and the team is credited on the checker’s page. The colour data comes from that project.
What you can do
- Choose from 180 RAL Classic colours, by number and name.
- See the light reflectance value (LRV) of each colour and the difference between them, with a pass or fail against a difference of 30.
- See the WCAG contrast ratio of the same pair, for when the colours are used on a screen.
- Swap background and object with one button.
The hard parts
Two kinds of contrast. On a screen, contrast is about light the screen gives off. On a wall, a door or a sign, it is about light the surface reflects. The checker shows both, and says which one applies where: a difference of 30 light reflectance points is the pass mark for physical accessibility, and the WCAG ratio is for on-screen use.
One checker, used everywhere. It is a single web component with no dependencies and all 180 colours built in. Any page can load it with one line, and the page on reddy.world loads it live from that library.
