Checkboxes and radios that fail validation do not get a red border

In Drupal 7 default behavior for a field which fails validation is to show a red border.

For example if the field is required but no input was supplied. This does not work for checkboxes, however.

EDIT: At request for clarification for desired behavior: The desired behavior is that checkboxes which fail validation should also show with a red border.

This is because the "error" class gets added to the input field, but checkboxes and radios don't let you style borders.

How can I make it work for these elements too?

Since checkboxes have the "error" class, you need to use the :has() pseudo-element on its parent wrapper:

.form-checkboxes:has(.error) {
  border: 1px solid #c00;
}

The result: