Include alt text

Use alternative text (alt text) for images, logos, drawings, and other graphics. Without alt text, screen reader users just hear "image." Some images automatically include alt text, so it's a good idea to check that the alt text is what you want.

Add or edit alt text

1. Select the image or logo.

2. Go to More editing options   Add alt text.

3. Enter alt text in the description field.

Use high-color contrast

High color contrast makes text and images easier to read and comprehend. Web Content Accessibility Guidelines (WCAG) 2.0 recommend a minimum ratio of 4.5:1 for large text and 7:1 for other text and images. For example, avoid light gray text on a white background.

You can use Chrome DevTools to review suggestions for increasing color contrast and apply them to your site.

Use informative link text

Screen readers can scan for links, so informative link text is helpful. It's best to use the title of the page as the linked text. For example, if you're linking to your profile page, the link text should say "my profile," not "click here" or the full URL.

Check text size and alignment

To make your site easy to read, use large, left-aligned text when possible. 

Justified text is more difficult to read because of extra space between the words.

Use text to support formatting

It's best not to rely on visual formatting alone to communicate meaning. Screen readers might not announce formatting changes, such as boldface or highlighting. For example, to mark an important section of text, add the word "Important."

Use numbered and bulleted lists

Google Docs and Google Slides automatically detect and format some lists for accessibility. For example, if you start a new line in your document by typing the number 1 followed by a period, the new line automatically becomes the first item in a numbered list. Learn how to format bulleted and numbered lists.

Source: https://support.google.com/sites/answer