TYPO3 Core

The form inputs and selects in the Edit section have an insufficient contrast ratio of 2.37:1 (border color: #6DAAE0, background color #FAFAFA), see WebAIM Color Contrast Checker

The elements get a subtle box-shadow and the border-color changes from #6DAAE0 to #4392D7, which is an insufficient contrast change from 1.33:1, see WebAIM Color Contrast Checker

.has-change .form-control {
  border: 1px solid #6daae0;
}

.has-change .form-control:focus {
  border-color: #4392d7;
}

Recommendation:
To fulfill the minimum contrast ratio for form elements, implement the following:

• Increase the contrast ratio of the border color for the form elements to a minimum value of 3:1.
• Increase the contrast ratio of the border color for the focussed form to a minimum value of 3:1.