I have a form with required checkboxes highlighted in red.
Checkboxes are particularly difficult to program like a text field. First off, there are only two values, on and off, so how do you validate that? Second, while a checkbox has a validation and calculation script, they are not accessible from the Acrobat UI.
So I'm assuming that this if for something like "I agree to the terms" check box? You could use the mouse up event to check the value of the checkbox.
event.target.borderColor = (event.target.value == "Yes")?color.black:color.red;
this.getField("MyCheck").setAction("Validate","event.willCommit || (event.target.borderColor = (event.value == \"Yes\")?color.black:color.red);");
Where "MyCheck" is the name of your checkbox field