Charts, graphs and maps use visuals to convey complex images to users. But since they are images, they provide serious accessibility issues to color blind users and users of screen readers. 

Sometimes explaining what the chart is about it may be difficult to provide a thorough explanation of all values and how they relate to each other.

Here are some tips:

• Provide a text equivalent for each non-text element, write only the information that is relevant to the content being conveyed
• Supplement color coding of charts with texture, differences in line style, text in graphs or shades of one color to improve accessibility
• Provide an accompanying text data table of the information in the chart