WCAG20 Guideline 1.4 Distinguishable
Guideline 1.4 Distinguishable: Make it easier for users to see and hear content including separating foreground from background.
Guidelines on color and contrast
1.4.1 Use of Color
Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. (Level A)
Note: This success criterion addresses color perception specifically. Other forms of perception are covered in Guideline 1.3 including programmatic access to color and other visual presentation coding.
1.4.3 Contrast (Minimum)
The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following: (Level AA)
Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.
Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.
1.4.6 Contrast (Enhanced)
The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following: (Level AAA)
Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 4.5:1;
Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.
Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.
1.4.8 Visual Presentation
Visual Presentation: For the visual presentation of blocks of text, a mechanism is available to achieve the following: (Level AAA)
- Foreground and background colors can be selected by the user.
- Width is no more than 80 characters or glyphs (40 if CJK).
- Text is not justified (aligned to both the left and the right margins).
- Line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing
- Text can be resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text on a full-screen window.