fiskeben

This plugin adds a simple way to let your readers enable or disable a high contrast stylesheet for the visually impaired.
Once a reader enables the high contrast stylesheet the setting will be stored in a cookie which means the setting will not only stay one when navigating to other pages but it will also be on when the reader returns.

Vividly

Enables toggling an extra stylesheet with high contrast CSS for visually impaired users.

Ishita Ray

Accessibility Toolbar adds a floating button panel to any WordPress website, letting users: 
– Increase and decrease font size 
– Toggle high-contrast mode for better readability 
– Customize colors from backend settings

ITY Accessibility Toolbar

Adds a simple accessibility toolbar for changing font sizes and toggling high-contrast mode.

Vividly vs ITY Accessibility Toolbar