Use of Color and Contrast
Color must not be used as the sole means of conveying meaning or content. When using color to differentiate elements, also provide additional identification that does not rely on color perception.
Example: Use an asterisk in addition to color to indicate a require form field
Example: Use of labels to distinguish colors
Text is much easier to read when there is sufficient contrast between the text and the background. Black text over white background is the de facto standard for both print and web. There will be situation where this combination is not suitable for all users. There will be users with various requirement, user with low vision may set their background to black and the text to either white or yellow; user with dyslexia may set their background to an off-white or light yellow and black text.
Since we cannot control the behavior of our users or what they decide to do with the adjustment, our main concern is to ensure that our website has a high degree of contrast for the general users.