The call to action button on service provider pages should be implemented using standard web technology that allows communication with assistive technology. Specifically:
Button label and text should be available to screen readers and have high color contrast.
Users must be able to navigate to and activate the button using only a keyboard.
The button should be placed in a logical location; assistive technology users should be able to reach the button with a logical sequence of steps.
Color contrast between text and graphics should pass a minimum of AA compliance to make the button visually accessible for the widest possible user audience. Use WebAim.org’s tool to test text and graphic color contrast by hex#.
According to WebAim, 13px is the minimum text size that should be used anywhere on the site, and 16-18 px is optimal for body copy.