There is not a built-in setting that I know of in 12 do darken the fields.  My understanding is they become disabled when saving to the repository.  I used this CSS and it has helped with the same issue: 

input[disabled][type="radio"]:checked::before {
	content: "\25C9";
  	position: relative;
  	z-index: 100;
  	top: -3px;
  	left: .5px;
}

input[type="radio"]:checked + .option-label, input[type="checkbox"]:checked + .option-label {
  font-weight: 600;
}

input[disabled][type="checkbox"]:checked::before {
	content: "\2611";
  	position: relative;
  	background: white;
  	font-size: 17px;
  	top: -7px;
  	left: .5px;
  	font-weight: 600;
}