If you have default settings on Wikipedia, and are reading this page on a screen, then you probably can't read the following:
- This is a secret message
because it has blue text on a blue background.
Text that you probably can read, such as red on green, may present a similar problem to people who have colour-blindness.
Text with low contrast, such as light grey on dark grey, presents a similar problem to people with other eyesight-related conditions.
The more severe their condition, the higher the contrast has to be for them to be able to read it.
Our non discrimination policy is
"approved by the Wikimedia Foundation Board of Trustees to apply to all Wikimedia projects. It may not be circumvented, eroded, or ignored by local policies."
"The Wikimedia Foundation prohibits discrimination against current or prospective users... on the basis of... disability".
To avoid these problems, you should ensure that text meets the guidelines set out in WP:COLOUR.
Snook's Colour Contrast Check provides a comprehensive check of whether a particular choice of foreground and background colours meets WCAG 2.0 standards for brightness difference, colour difference and contrast ratio.
You can find the text colour and background colour as a hexadecimal value by using the "Inspect element" function that most modern browsers provide. The default colour for blue-linked text with the Vector skin is #0645AD () and for visited links is #0B0080 ( ). Both should always be checked in addition to black (#000000) against any proposed background colour in case links are added later.