Is there a standard for indicating a high contrast style? [closed]

1. What is an acceptable contrast ratio?
2. Why is high contrast accessibility?
3. What's the recommended color contrast ratio of the level AA for headings?
4. Why is high contrast an issue to be considered on mobile?

What is an acceptable contrast ratio?

Color Contrast Ratios Guidance

Whenever using color in images, ensure that the colors have a contrast ratio of at least 4.5:1. This ensures that the text is still readable to those who may have color blindness.

Why is high contrast accessibility?

Built in accessibility features such as Windows High Contrast Mode are important because they allow people with access needs to use devices without purchasing additional assistive technologies such as screen magnifiers.

What's the recommended color contrast ratio of the level AA for headings?

3 Contrast (Minimum) (Level AA): The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following: Large Text. Large-scale text and images of large-scale text have a contrast ratio of at least 3:1; Incidental.

Why is high contrast an issue to be considered on mobile?

Reading text on a smartphone screen can be be difficult for people with weak vision. Often, light grey text tends to merge with the background making it difficult to read. An easy way to solve this issue is by enabling high contrast text from Settings > Accessibility.